sounds like a great idea. Ask some of the guys here on the boards for info on the 460's. Greg Cook and Chilly460 really know their stuff when it comes to big blocks. Also, I think there's another forum dedicated to big blocks.
I did this on my 351C 73 Mach1with minimal trouble. I used a 74 460 with C6 from a Torino. The Torino C6 was the short-tailshaft one so I didnt even need to cut my driveshaft. Motor mounts on a big block utilize a plate and an insulator. I used the plates from the Torino and I believe got the insulators from one of the Mustang vendors for a 70 429 application. In stock form, these are torque monsters but you are not really going to really start running hard at the drags until you work over the motor a bit. It doesnt take much with that much displacement to get a good runner. I have a mild buildup on my 74 460 and went from running about 15 flat with the 351C to mid 12's on slicks.
Be glad to help if I can,
Well, much of this depends on your intended use for the car. If you just want a fun street machine, then the 8 inch rear will be fine with regular street tires. If you want to use slicks, may want to look into a 9 inch. Is that a 4 speed toploader gearbox? If so, it is a strong beast but will require a bellhousing for the 460 pattern. If it is a 3 speed, well they are reasonably strong (just not as good gear spread as the 4 speed).
I haven't been able to get a straight answer on this yet myself, but I do know that your smallblock tranny has a longer input shaft than the bigblock tranny.I have heard you must change the input shaft or shorten it to use with the bigblock