finally got it. tried a punch and 3lbs sledge and just butchered the edges. tried a bolt, grinded the end into a pentagon and hammered it in, nothing just slipped, took the 3/8 extension, again, and put it in so it lined up exactly like it shouldn, corners of extension on flat (or what appeared like it used to be the flat side) and hammed it in with the same 3lb hammer and finall got it. guess, i'll either get a new one, or cut that one for a 1/2" drive. . .
thanks anyway.