Welcome!
You don't say if you have the regular 301, or the Turbo model.
Either way, the 455 should drop in with no problems.
I believe the mounts are the same, but not 100% sure.
As already stated, the car will always be worth more stock, and with the stock numbers matching engine.
But, nothing wrong with just keeping the original motor off to the side.

The tranny won't last, if you have a lead foot, and the rear end should, as it's pretty much the same rear as the cars that came with the 455.
A great place to read and talk about the 301 engine, is:
301 Garage
If you get a chance, post a few photos of your car in the 301 section on this site.
Hope this helps,
:beach: