I recently purchased a 1998 Chevy four-door dualie at auction for $800. I do a lot of towing, whether it's my camp trailer or my gooseneck hauling firewood or my trail rig. However, upon getting it home I discovered that the engine is seized. My problem is finding a replacement engine. The cheapest used one that I can find in wrecking yards is $1,500. Will an older block work with the Vortec heads? I have a buddy that has a mid-1980s 454. Can I put the Vortec heads, intake, accessories, and everything else on this short block and it will work OK in the truck? Or does it have to be specifically from that era of Vortec engines? As a secondary option, could I pull a 350 out of a vehicle and put it in this one and have everything work fine as long as I change the computer? I did this once with a TBI fuel-injected truck, but I wonder if I could do it with this 1998 without having to mess with wiring.
The short answer is yes, your big-block swap will work if you do exactly as you say and swap everything from the Vortec engine onto the 1980s-era short block. Vortec heads are compatible with earlier-generation blocks, but there are a couple of differences. The Vortec heads use center-bolt valve covers, and the bolt pattern and angle of the intake manifold surface are different. Other than that, everything else should work fine. The Vortec heads should actually help the earlier engine breathe easier and pick up a decent amount of power. About 20 years ago we took a brand-new ZZ4 small-block crate engine with nice GM Performance Parts aluminum heads and swapped them for a pair of box-stock cast-iron Vortec heads. With no changes other than the head swap, we picked up almost 50 horsepower on the dyno. Obviously the Vortec heads are going to be compatible with the truck’s existing intake manifold, but there is some performance benefit to using the heads as well. All of the later accessories should work fine on the newer engine, but make sure you use the correct later reverse-rotation water pump, as the serpentine system spins the water pump in the opposite direction than earlier V-belt systems.
As for your small-block swap, we are not 100 percent sure. While a TBI engine wouldn’t be a big deal, there is not as much information about the differences of the later Votec EFI system between small- and big-block engines. Because the later system is more complicated, it seems likely that you will run across more issues than just the computer. Plus, there is the reduction of torque. Since it sounds like you plan on working the truck, we think you would really miss the torque of a big-block. Since the truck is already equipped with a big-block, we’d probably keep it that way.