I agree that the difference between the length of a rigid fork and a 1994 suspension fork will be minimal... and in 1994, I'm sure a lot of companies were simply slapping short-travel forks on the standard frame without any alteration from the rigid fork geometry.

I would go ahead and put the rigid fork on. If it does not work as you want you can re-sell it, and last I checked, new rigid forks can be purchased from the LBS for ~$50