Here's a photo of it in it's original G.I. configuration. A late WWII Remington Rand 1911-A1. No modifications have been done that can't be reversed in just 20 min. to restore it back to it's original G.I. self.
Here's the first Commander conversion attempted with a 1991-A1 slide assy. The firing pin block must be removed from the '80 series and later Colt slides in order to fire on these older frames. The Colt barrel proved to have a very tight chamber and unsuitable for cast bullet feeding reliability.
Same slide assy shown with a full size Springfield Armory slide assy I built up for this gun twenty years ago with a Wilson Combat barrel.
Here's the final product of my alteration. A pre'70 Colt Commander slide mated with an Ed Brown match barrel on the Remington Rand G.I. slide. Function is flawless and accuracy outstanding with this combination. The holster is a "Blackhawk" inside the pants holster made in Italy.
I'll say this on building a Commander on a standard size frame, if you start with just a slide, firing pin, stop, spring, and extractor from a standard slide will fit fine, of course the barrel is shorter, and requires a shorter spring, bushing, and plunger. If a Commander hammer is used, a Commander grip safety is also needed, mine uses a G.I. grip safety modified to clear the Commander hammer, all other frame parts are the same as a standard 1911/1911-A1.