Series 80. 1991A1 Compact. Same size as the Officer'* model (3.5" barrel....this is my primary carry piece). The only thing left Colt on it is the fram and slide, though. All other parts are Wilson Combat. This is the first of several like it I've built, getting ready to do another for a friend. You can build a $2k pistol for $800 this way.
I've got a bit of experience. I grew up with firearms, then had some time in the Marines. Been building and shooting ever since.
Mods to the pistol:
Full-length guide-rod with reverse plug. Required machining the slide apron.
Modified ejection port (machined)
High-ride Beaveartail grip safety (machined frame)
Lightweight adjustable trigger, WC sear
WC mainspring housing, changed spring weight
Hand stippled front strap
Extended slide release
Extended mag release
Ambi extended thumb safety
Funnelled mag well (machined frame)
Custom finish (teflon moly baked on finish)
Custom Ebony grips
And on and on.....I forget it all without the pistol pulled apart in front of me.