Scrap the non-PRG stuff, then take the PRG version and call it 'specification'? ;-)

You could try to 'flatten' the VCX and the SCX into text via SCCTEXT and then compare the three versions (diffing tools can be set to ignore differences due to whitespace and case) but quite probably the results won't be pretty.

The PRG version is probably the easiest of all three to reverse-engineer (to recover the spec or bring it up to date). But some of the differences in the other versions may have crept in there for a reason and if the WinDiff approach doesn't work you'll have to take a programmer and call him Diffie, unless you want to lose that knowledge.