Here's the only place where things got a little tricky. Ford used a separate spacer sleeve on the crankshaft between the harmonic balancer and timing gear. Externally balanced engines from '79-up used this spacer (shown) with a balance weight (Ford PN D9TZ-6359-A). A matching weight on the flywheel/ flexplate put the engine into balance. With our engine already internally balanced at Speed-O-Motive, we needed a spacer sleeve sans balance weight from a '78-or-earlier big-block, which we couldn't find. So, being the garage "innovators" we are, we cut and ground the counterweight of our late-model spacer down to neutral balance.