This is the crankshaft harmonic damper retaining bolt from my 89 Formula 350 TPI engine. I believe this was the original bolt and harmonic damper. The bolt measures 2 1/4 inch long but looks like it only engages the threads for about 1/2 inch and was starting to strip. From what I could find this 2 1/4 inch long bolt is the correct spec. To be safe I purchased a 2 1/2 inch and a 3 inch long (grade 8) and checked install depth. The 3 inch was too long but the 2 1/2 inch threaded in far enough so I used it (torqued to the spec in gm manual) to retain the new damper.
Has anyone else run into this? If so what was done to correct?

 

You used a 7/16-20 grade 8 bolt to retain the balancer, didn't bottom it out in the tapped hole, and torqued it to spec. That's about all anyone can do. Small depth variations could be addressed with various thickness washers for a balancer hub if needed for things such as aftermarket parts, added pulleys, etc., but you can stop second-guessing it and move forward.