I found slide/barrel/springs combos this weekend for almost nothing and need help identifying one of them.

I got a polished SS. Colt Mark IV Gold Cup match(just top half of gun) in 38 Super.

I got a Blued Colt Govt model 38 Super.

Lastly, the one I have a question with on that has "El Centauro" stamped on the side. It is polished SS and is in 45acp. It has the exact same Horse the the Gold Cup(Colts in general have)slide has on it stamped on the same. I can't find out anything about it though. Theres nothing else stamped on it other then El Centauro and the horse.

The last question is do you guys know where I can find cheap used or just low price receivers for 1911's so I can put these together?