For a 67...I'll be looking to buy a complete rear assy, drum to drum with a posi rear....low 3s in gearing. what donor vehicles can supply a direct complete bolt in? any pitfalls?

Any other A body cars from 64-72 such as a GTO,Impala,Tempest,Cutlass, another Chevelle, and several others that I'm not thinking of. As far as pitfalls I think all the bracketry and the width is close to the same on all of these but I'm not 100% sure. My 12 bolt came out of an early 70's Cutlass and it bolted right in but the rearend is about an inch wider than the factory one.

64-67 uses a shorter rear than 68-72. You need to decide if you want a 10 or 12 bolt. 12's are getting harder to find for those years.

The '67 is all by itself in the rear end. It is the same width as the '65 and '66, but it has the same spring perches as the '68 to '72. You can use any of these, but the later rear ends are 1 inch wider over all, 1/2 inch per side.