EDIT: WOOPS!! I mis-read this as a 1911 and not a 625!! As such, the information below probably doesn't apply, except for the part about the reloads and brass. 460 Rowland brass is probably RARER than 41 Action Express brass, and impossible to find, and pricey if you do find it. 45 Super brass and moon clips would be the way I would go.To begin with, here's the scoop on the 460 Rowland:
http://en.wikipedia.org/wiki/.460_Rowland The case is NOT the same size as a 45 ACP or 45 Super, so you will need to get a 45 ACP barrel (1911 45 ACP barrels are cheap and plentiful) for the gun. As it stands, the gun you have is pretty rare and collectable, so hang onto the 460 barrel in case you ever want to sell the gun. I WOULD definitely get the 45 ACP barrel, because it's my personal opinion that the 1911 really can't handle a steady diet of 44 magnum strength loads and survive. The evidence?? Try and buy a LAR Grizzly in 50 AE or 45 Winchester magnum. You won't have much success, because most of these have given up the ghost and succumbed to frame cracking, even with the beefed-up frame of the LAR design. The 10mm and the 50 GI are about the most potent loads you can run in a stock 1911, and trying to go higher than that will put too much stress on the gun.
The 45 Super is a hell of a lot more powerful than a 45 ACP +P load, and the "factory spec" from Ace Custom Guns (home of the 45 Super) is a 230 grain bullet at 1200 FPS. There isn't a 45 +P load that can come close to that, and I have no idea what you can do with the 185 grain bullets in a 5" barrel. In my EAA 45 gun that I have worked up to 45 Super, the 185 grain bullets come out the front at 1260 FPS, and that's with a 4.4" barrel! In addition, 45 Super brass is easy to get (John-Boy has a whole box full of it), and it's not too expensive. Good luck finding any 460 Rowland brass at all. Power Pistol is THE powder for the 45 Super. The recoil spring that came with the 460 Rowland barrel should work with a 45 Super load if it's hot enough, and you can always buy a slightly weaker spring (22# - 24#) if it doesn't.