Keep your eyes peeled for an older, used Springfield Armory 1911, the ones with the serial numbers that begin with "NM".
They are my preference for building a "custom" 1911.
They were made with slightly more metal in the wear surfaces such as frame and slide rails and the pin holes tend to be on the tight side.
They were more utilitarian than racy and tend not to be beat up when you find them.
I have built two 1911's with these and they were my primary carry weapons through a large part of my LE career.
My full-size had roughly 7,500-8,000 rounds of full power ammo through it before I put a Nowlin bushingless barrel in it. It is still tight and runs perfectly.
The other one is an Officers Model frame with a Commander slide and barrel giving me the slightly longer sight radius but the shorter butt which aids in concealment.
For students of the 1911, I highly recommend THE best first book to get is Jerry Kuhnhausen's 1911 Shop Manual.
You can buy it new on Amazon for just over $50 or go to Abe Books website and pick up a like-new copy for about $35.
Ed