Me thinks the only difference might be the feed ramp, because I think the ejectors are the same or similar enough for the slides to interchange
A .45 slide and a .38 Super/9mm slide will interchange on a Commander, but not on the Gov't Model.
I actually just traded a friend Smith and Wesson 1911 for this like new Colt. I like 9mm, just not as much as 45. I will probably just trade this gun to someone for a 3" 1911 in 45, with sights! This is a fun little gun, but not liking the trench sights. I would never put the Ruger slide on the Colt frame, just sounded interesting. (actually I tried it after reading that on here, but a series 80 frame on a series 70 style slide would scare me, and the dust cover on the frame is too short.
The ejector for the .45 and 9mm are different; the 9mm ejector is longer and thinner. Also, you may have to change the slide stop.
I actually went the different route, I used an Essex .45ACP frame and mounted a complete Colt Series 70 GM 9mm slide group. I changed out the both the slide stop and ejector, and was good to go.
I also used a RIA .45ACP compact frame to build a .38 Super CCO using a Series 80 Enchanced Combat Commander slide and Storm Lake barrel. I had to narrow the ejector to fit the slide, but the length was good as both the .45ACP and .38 Super are the same length. I didn't even have to change the slide stop.
Of course, you'll also have to get the right magazines and I'd suggest the right weight of recoil and mainspring.