How did I do the wiring? Holy moley. Well first off I have done wiring for about 12 different conversions to date, most of them 4.0L.
This was my first EEC-V system.
The key is to have the complete wiring schematics books for both vehicles.
Then its just hours and hours of tracing wires, researching where and why, piecing it all together, sleepless nights with dreams of wiring looms, and lots and LOTS of back breaking soldering.
It is not uncommon to have more time in the wiring harness then the actual conversion.
I think I had like 100 or so hours in this harness.
I was really happy to work with the 5.0L harness however, it is a stand alone drivetrain harness, which is nice for a change. the stupid 4.0L OHV harness has the headlights, ABS, power distribution, and a bunch of other junk wrapped up with it. The 5.0L goes from computer to engine and trans, and from computer to truck, tweo big plugs, much much easier.
Dont be scared of OBD-II. There were only a few extra sensors to deal with (fuel tank, EVAC system) In 98 they started using PATS< which means you need to re-flash the PCM to remove it or get the PATS module and key swtich from your donor.
I am loving this OBD-II system and cannot WAIT to get a laptop interface and tuner.
the EFI 5.0L you are talking about is MUCH easier to wire then what I went through. That speed density 5.0l can and has been put into everything (toyots trucks, Miata's, etc) Painless makes a wiring harness you can use, or you can do it yourself (dont be scared) Just make sure you get the wiring book for the 250 and the T bird.
what engine does the 80 250 have now? I-6?