There is a round called the 45 ACP+, which is rated below the 45 Super, which is rated below the 45 Rowland, which is rated at/below the 45-08 (45 ACP brass formed from 308 cases) as far as pressures, and thus velocities. I've seen some sources rating a 260gr slug at 1200 fps, perfect for backwoods protection.
All use 45 ACP external case dimensions, just the inside dimensions are different, thicker web, smaller primer pocket, etc. to allow higher pressure loads.
Usually the only change to the gun required, as long as the steel of the firearm is rated for it, is stronger recoil spring and something called a shock-buffer.
Funnily enough, south of the border, Norinco frames and barrels are among a select few with steel quality rated for these upgrades.
Of course all of this info is from the internet; multiple sources but still, the internet

There's an old thread on here somewhere about turning a norinco double stack 45 into the 45-08, and how to form the brass.