The frame is the actual "firearm" so that isn't really a replaceable "part". You would actually be buying a different "gun" and using the parts off your existing gun to complete the "new" gun.
Mag "well" is part of the frame, mag "guide" is replaceable.
AKAIK the PT1911 is the same as any other 1911, so parts like the mag well guide and hammer should be interchangeable, but someone that knows for sure will have to comment on that.
Why do you want a lanyard loop?