Just saw your post while researching a '97 Colt 1991A1 Protector I just put in layaway. Talked to Greg at Wilson who said that they were using both Colt and Springfield Armory frame/slide kits in 1997. The one I am buying is black Armor-Tuff, Commander slide, Officer's Model frame, night sights, 30 lpi frontstrap, 20 lpi main spring housing, aluminum speed trigger, single thumb safety, standard recoil spring guide.
For those interested - I took my Colt 1991A1 based Service Grade Protector Compact to the range Monday. I'm impressed. It will hold the Ten Ring of an NRA 25 yard timed and rapid fire target. I did not expect this level of accuracy as the gun is not tight. The slide to frame fit is pretty much what you would expect with a stock 1991A1 and I can turn and remove the barrel bushing with my fingers. It is a service grade gun with the kind of fit that makes for easy take down and reliability, but produces match quality accuracy. The commander slide on the officer's model frame preserves the proportions of the traditional 1911 in a smaller package - I'm a happy camper