Originally Posted by
EjustE
check the spacing of the rear, if it is less that 130mm you cannot have an MTB 7 freewheel there and it is probably the frame that is the problem and not the RD
Shimano makes a 126mm spaced 7-speed freehub. OP didn't specify whether it was a Freewheel or Freehub but I assumed Freehub as it was stated to be 'early 90's'.
As long as the wheel is in the dropouts enough for the Skewer or Bolt to get a good solid grip you should be able to safely put the wheel pretty much wherever you want in the drops.
I think i might try this whole moving the wheel forward business and see for myself if I can tell the difference. If its one of those 'princess and the pea' kinda things though I will fail the test.