A lot (okay, most) of the civi Colts had the larger screws up front, but if its a surplus upper (and I think LE uppers as well), it will be milspec, and will work on any milspec lower (basicly, anything other other than a civi colt that uses the screws).
The funny thing about the offset pin in the link above is that it says its to use large hole uppers with mil-spec lowers, however in the pic its for mil-spec uppers on large hole lowers. If you order it, you might wanna call first.
M60Joe might be able to install a bushing in a large hole upper so it will mate to a milspec lower using a standard pivot pin. There are pics on his site of bushings installed in lowers, but I dont recall seeing any of uppers.