I put '73 Volare (A body) discs on my '71 Challenger and they work great, but you will HAVE to mount the calipers in the front. Just requires a switch in sides of the spindles. If you don't, the calipers will hit the shock on every turn. Alignment is not an issue, mine was able to be aligned...
The tension is going to feel like a lot with the trunk lid not installed. I'd be willing to bet if you bolt it on it won't come up as fast as you think.