Hello guys, i am in the process of doing an engine swap, putting a 1994 351w into 1990 f250. what i am noticing is that most of the connections are all the same besides, the 1994 had a distribution box, and the 1990 just has a big clump of wires and connections. How is it that i use the 1990 f250's wiring for the '94 351w. please any help guys.

 

You unhook all the wiring from the 94 motor and leave it in the truck it come from, and you reuse all the existing wiring from the 90. Its that easy.
All you're using is the motor and probably the distributor. You'll need to use the 90 distributor because the tfi module is on it for he 90 and on fender of the 94. You'll need to swap distributor gears if the 94 is a roller motor though.

 

+1.. strip that '94 of all the wiring and use only what came with your truck. Only other changes are the plug firing order and if you use the '90 distributor(you should) you just need to put the steel drive gear on it from the '94.. because that motor has a steel roller cam in it that needs a steel distributor gear.