I like computers but they're a tool, not some hipster doofiis's pathetic life.
Macs are great computers but that's all they are, to these wannabee hipsters, it's their lifestyle, pretty sad.
Have you though of putting in a 340? I think they were only available for two years but they rock for an A engine. I'm pretty sure that Mopar never put matching numbers in their vehicles ( I could be wrong on that) so while you should keep the 270, a 340 kicks some serious *ss and doesn't weigh a ton like the B motors, 383, 413, 426 Hemi or normal. You could put in a B motor but it requires welding in a new crossmember and if you go the 426 Hemi route, those things weigh a ton. A 440 six pack puts out 420 Hp and the hemi puts out 425 and weighs a ton and due to the long length of the exhaust rocker arms, it has a low redline. Of course everyone knows the manufacturers were lying about their HP numbers to fool insurance companies but it didn't work.
I would consider putting in disks on the rear, the job is reversible although I wonder how they deal with the parking brake. C3 Vettes had 4 wheels disks but the emergency brakes were drums inside the rotor hat.
Unless you're going for competition then everything has to be as it left the factory including the chalk marks on the pumpkin, tranny and other places and of course, you need the correct bias ply tires. I'd like to see some pics. 60s Mopars as well as other manufacturers were some awesome vehicles. Too bad Mopar stopped making Challengers and Cudas in 1973.