Thanks both of you for the info.
I found both Millet and Pachmayer adjustable sights that fit in the existing dovetail without machining, so I'm going to try one of them first.
So AeroE, if you read this, please don't go to any trouble to find numbers because I may not need them.
Hopefully I won't need them ... I am learning a lot about my 1911 as I'm replacing the trigger, hammer and sear myself. When I'm done it'll be very neat - I already have a 400 Cor-Bon barrel with a recoil compensator on it, and more powerful springs, so when it's all done I'll post some pictures of the beast.