The good news is you have a 63 Classic. In 63 there was no V-8 for the Classic at first, but the more up-scale Ambassador used the same body with up-scale trim and AMC's first generation AMC V-8. It was only a 327, but external dimensions and weight aren't far from a big block Chevy. A smaller bore 287 was made available in the Classic in late 63 due to dealers complaining.
The six cylinder used in the 63 Classic sits directly on the crossmember, so you'll have to fabricate perches and mounts. There's plenty room under the hood of the Classic, and you can get a set of V-8 springs. You definitely need stronger springs in the front end -- otherwise the stock front suspension is fine. You'll want power steering also. It's not hard to mount a standard Chevy power steering box.
The rear suspension has to be changed along with the transmission, but you knew the tranny had to go. It's not hard to change the rear suspension, but takes some work. Keep the coil springs in their factory location. The spring seats bolt on top of the axle. Drill the tubes of the donor axle for the 3/8" fine thread bolts and use the original seats and rear springs. The shock mounts can probably be used also. The spring location makes it easy to air bag these cars, even on the front. They use regular coil springs with shocks mounted outside the springs, not coil overs. A Ford Explorer rear axle is about the right width and will have the same 5x4.5" bolt pattern as the front. You'll just need to locate the axle. Ladder bars are easy, but universal mount four links aren't much harder. The real trick and easy setup is to adapt a G-body "truck arm" kit from Hot Rods to Hell (
http://www.hotrodstohell.net/truckarm/truckarm_gbody/truckarm_gbody.htm). Heck, a G-body axle is close to the right width also, but then you have that Chevy bolt pattern on the back, AMC/Chrysler/Ford on the front. I have that problem with my Jaguar rear axle, I just use dual pattern wheels.
The question is, how much work and money are you willing to put into the car? It's not a simple swap, but it's not real complicated either. There's just more that has to be done, and nothing is a simple bolt in -- fabrication and welding required!
