The 45ACP or 45 Super can be done on a Savage, but only as a single shot. Also it should be said that if you build a 45ACP barrel you cannot shoot 45 Super in it, and if you build a 45 Super barrel you cannot shoot 45ACP in it. These type of barrels headspace on the case's mouth and due to the difference in the case lengths of these two rounds they cannot be interchanged.

As foxx said, the 450 Bushmaster is a much better choice as it feeds easily from Savage magazines and has a bit more thump to it, and it can be loaded down to subsonic levels if needed.
Jim at www.apachegunworks.com is the place to get a 450 Bushmaster, and I am sure he would make you a 45ACP or 45 Super if you really wanted.