Does anybody know if rotors and spindles will work on a 72 ss chevelle from a 77 nova?

I'm not sure about the nova spindles, but you can use metric car spindles if you ream the lower ball joint hole to the chevelle size. A stock car buddy of mine uses chevelle frame stubs on the dirt track modifieds he builds. He uses camaro spindles and reams them to fit. If your concerned about weight, the metric car stuff weighs less than the camaro stuff. In fact the metric car brakes weigh the same a the stock drum brakes. By metric car I mean 78-88 monte carlo, malibu, cutlass, and regal.
Circle track guys also have the rear disc thing figured out. I found a set of rear caliper brackets at the local dirt track supplier for 15 bucks each. They use metric car front calipers and mounting hardware. Front rotors off a '93ish Jeep wrangler have a nice deep hat and are real close to the right diameter. They just need to be redrilled to the 4 3/4 bolt pattern. Been running this setup for 2 years and it seems to work well, even with the manual brakes.