Maybe somebody will come along and post the wiring schematics for the '98's donor truck power windows. I don't know squat about anything '95 and newer, but something in the back of my head (those damn voices again) is saying that Ford may have starting using power window relays sometime after they started using the GEM, and then the SJB (Generic Electrical Module and Smart Junction Box).
IF that turns out to be the case, you're dealing with two different circuit types, but you can still get around it by adding your own relays so that the '98 switches can drive the '94 window motors.
A '98 schematic would be super helpful here. A picture of your '98 switches, from the backside, and the '98 wiring connector (if you have them) would help some too.
And, welcome to TRS. I'm up the road from you, in Bowdon.