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1971 GMC Po Boy Prerunner Project

1971 Gmc 3 4 Ton Pickup
Agustin Jimenez
| Staff Editor
Posted July 1, 2012
Photographers: Isabel Jimenez

Building a Go-Fast Classic on a Budget

I’ve never owned a GM product before, but I’d been itching to get my hands on my own GM truck to build into a go-fast budget wheeler. I scoured the classifieds for a worthy candidate (cheap running truck) to build. My plan was to go with a ‘73-to-‘87 Chevy 3/4-ton 2WD pick up for affordability and reliability.

Of course that all changed when I spotted this clean, solid body ’71 GMC 3/4-ton pickup for $1,000! The truck had been sitting for at least a year in the Southern California high desert just waiting to get built into an awesome truck.

The Motive


I’d always liked that body style ever since I saw the black C-10 in Dazed and Confused trying to blow the doors off a Super Sport Chevelle. And for a thousand bucks, I’d be more than happy to work with this cooler classic. It had very little rust, was already primered, and was actually drivable when I arrived for an initial inspection. A deal was struck with the owner and I returned the next day to pick up OFF-ROAD’s new prerunner project truck.

I had good reason for choosing a 3/4-ton 2WD truck instead of a lighter half-ton. First, the 3/4-ton’s beefier frame is stronger, and I made sure to find one with a small-block instead of a big-block to help keep weight down. Second, the eight-lug drivetrain was bigger and would hold up better to the rigors of off-roading. While I could’ve swapped an eight-lug rear axle into a half-ton truck, I’d have been stuck with a weaker five-lug 2WD IFS on the front side. Lastly, I got a Dana 60 rear axle that I could keep with my ’71 3/4-ton purchase.

Parts and Suspension

I had to start with suspension first—not out of necessity, but instead to satisfy curiosity—I wanted to see my truck on my new 35-inch Mickey Thompsons with some drooping A-arms, and that seemed to take precedent over the radiator fix, seat fix, and some other stuff I needed to address before I could drive it.

Bolt-on suspension on a truck this old is a tough one—especially on a 2WD truck. I could build completely custom stuff, but that would be costly. After asking around and checking out some old magazines, I was astounded to find that Chassis Tech still has a bolt-in long-travel A-arm kit for 2WD ’65-to-’87 Chevy/GMC trucks.

We kept our rear suspension simple and used Chassis Tech’s shackle flip kit to add a bit of height to the rear of our GMC. Without cash for aftermarket leaf springs, I’m removing the upper overload packs and lower overload leafs on the original springs to soften up the ride. It goes without saying that we’re really excited to build up our Po’ Boy Prerunner so we can haul the mail in the dirt with this awesome classic truck.

Next Time

This is just the beginning of our newest project truck. The Po Boy Prerunner will no doubt get more expensive as I’m able to save up more money to buy parts for it. My plan in the beginning was to spend minimal dollars to build a beater that I could pound into the ground, but I’m already loving this truck and planning to dump more money into it. Perfect; I needed another money pit.

02. I really like the fact that my truck came with the small block 350ci V-8. Those engines are easy to work on and really cheap to rebuild and can make lots of power for practically a song.

The TH350 transmission behind our small-block isn’t quite as robust as the TH400, but it has a lower first gear and will be great for off-road fun as long as I add a good transmission cooler to it.

03. With almost no suspension options, I was elated to find that Chassis Tech still had a bolt-in A-arm suspension. The kit by itself is pretty basic—control arms that are three inches wider per side, new 3-inch lift coils, and new billet cross shafts. Chassis Tech also has brake lines, rear blocks, leaf springs, shocks, etc, so you can mix and match what you want. The Chassis Tech A-arms are stronger than the factory units and feature reinforced ball joint mounts to hold up to the abuse this thing will see in the desert. The upper A-arms are made of 1.5-inch, 0.156-wall DOM tubing and have reinforced ball joint mounts that are machined out of 1/2-inch steel plate. The lower A-arms are made of a heavy-duty 1.75-inch, 0.188-wall DOM tubing and feature 1/4-inch plating and spring perches as well as 1/2-inch steel plate machined lower ball joint mounts.

Photos

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07. With our newfound height we were able to install some larger rubber underneath our truck. We went with a set of 315/75R16 Mickey Thompson Baja ATZ radials because they feature a heavy-duty sidewall while still delivering excellent floatation in soft sand. I didn’t have to think twice about what wheels I wanted on this old school prerunner; I went with a set of 16x8 Mickey Thompson Classic Lock polished aluminum wheels (incidentally, these are the smallest wheels I could bolt on our truck over the brake package I had). These wheels are definitely perfect for any vintage off-road truck and the fact that they only weigh 24 pounds means we don’t have to worry about losing precious power from a heavy wheel-and-tire combination.

08. Rancho has recently released their new RS7000MT shock. The RS7000 is a nitrogen-charged monotube shock with a high-pressure gas charge that is separated from the internal oil to improve damping efficiency. The shocks use a heavy-duty, 14mm chrome piston rod and feature a 46mm bore and piston to smooth out rough dirt roads. They have a brushed finish with zinc plating and a clear coat to protect the finish on the shock body throughout its life.

The RS7000MT was the perfect shock for our Po Boy Prerunner—good quality and a nice firm ride while not costing much more than a typical OEM-style shock.

Photos

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12. You didn’t think we would forget about adding traction to the rear of this 2WD, did you? “Lincoln locking” the rear differential is the ultimate on-the-cheap solution for traction. And since this GMC project is budget minded, the low-to-no cost of welding the differential together was the only way to go. I stopped by for lunch with the guys at Custom Off Road Fab in Montebello, California, to get the Dana 60 Lincoln locked (but it was actually with a Miller welder) in less time than it took us to eat lunch. Now we can venture out in the dirt with plenty of confidence knowing our rear tires will be spinning together.

Sources

Rancho Suspension
Monroe, MI 48161
734-384-7804
www.gorancho.com
Chassis Tech
Mesa, AZ 85210
800-842-8789
www.airbagit.com
Custom Off Road Fab
323-568-6835
www.customoffroadfab.com

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