usp compact old vs sys7

[gotchya24]

so we know that the ns2/sys7 versions have different internals. most slides by shooters design are made for the system 7 version and not for the old one (the original).
my question is, if we have the old one, and we get a SD slide for the sys7s, could we just simply transfer the old original usp internals (from the slide) into the SD sys7 slide, slap it back onto the old one and make it work? or would there still be compatibility issues?

any help would be great..thanks!