Woody,
I believe your thinking is pretty straight. BB cars are always sought after, more so if you can prove what they are or how they were optioned. For the one with the missing engine, you can plan either way (modified or stock) and not really detract from the car or the value significantly, but the A/C car would likely be better restored if it indeed has a lot of the original equipment. Pretty desirable combination in my estimation. Both cars look like good candidates for restoration - nice find and a good purchase.
My BB SS L78 car is one of those that the NCRS paperwork skipped (12A '68 build). One week shy of the X codes, it's most saving grace is the original block is still with the car, but I would sure like to know what dealer it was sold through in Illinois. The search goes on - you can never find enough info on these cars, which is a lot of the fun in owning them. Good luck and keep us informed on what you discover, and send pics.
Regards,
Steve