Do a search for where you can find fms 3.73 gears the cheapest and take them to a trusty shop and have them installed.
www.oemfordparts.com has nice prices on stuff, but not sure of their gear prices. May wanna also have the trac lok rebuilt while the gears r going in. The kit is like $45. Then i'd do a full exhaust, longtubes being better, but thats up to you. A full tune up would be a smart thing to do before modifying it, plugs, fuel filter, wires cap, rotor, advance timing, remove silencer, change oil/trans fluid....