Be real careful of what starter and off starter solenoid set up that you have. The new starters have the solenoid built into the can on top of the starter with the one on the firewall being merely a relay for the start signal - and I don't have a clue when these were installed - mid '90s maybe. With the new setup you have 2 heavy wires on one terminal with a lighter one running to the starter - there being 2 wires rather then a single heavy one like the older Fords.
This is what I mean. The sketch on this page is NOT the solenoid I'm using - I'm using the older style, with some mods to my wiring