I just swapped my original BOP 8.2 for a GM 8.5. The 8.5 came from a 73 Nova. But I also swapped in a TH350 from a 78 Bandit Trans Am. The guy gave me his drive shaft, and guess what? It fits perfectly! One inch shorter! Which is what most people have found they need including me.

Now if you measure center to center on the u joints you will find it is too short, but look at this photo. The tip of the yokes are aligned, but the u joints are not. The second gen drive shaft on the right has more length to it before the slip portion of the yoke begins.

Center to center at the rear end in the second photo shows just slightly over one inch.

So before you go buying or modifying drive shafts, grab one from a second gen that had a TH350 transmission.

They fit!