So the wagon engine project is finished. The reassembly was done last week, but a driveability issue was making it run like crap.
Symptoms were: Idling too high (could unplug IAC, turn on the A/C, and put into Drive and not stall), Rich smell at idle, zero power at WOT, backfiring, misfiring, and bucking. Everything you want after you an engine back together and start it.
Anyway, finally had some time to get out and poke at it. Grabbed my handy paper clip and test light, and ran a KOEO test and got Code 23 for TPS out of range or set too high. Probed the wires to the TPS and got 1.48v. That's way too high. Ford likes it under 1.12v, .84-.99v is preferred, and apparently all the way down to .54v is acceptable. The TPS is slotted for some adjustment, but not that much, but I don't have a faulty TPS. It was checked out good on the old throttle body, so what gives? Well, these do have a throttle plate stop screw that really shouldn't be messed with, and the best Brian and I could come up with was it got knocked out place or fiddled with after it came off his Mustang. I turned out the stop screw while measuring voltage as it steadily dropped and tuned it to the precision point all the Mustang fanboys like at the just-oh-so-perfect point of .997v.
I also swapped all the plugs and wires. When putting the wires back on, it was clear many had lost their distinctive "click" you want when installing them. Figured it wouldn't hurt to do the plugs just in case despite being low mileage (and they looked the part). The old Autolites definitely had crud blown onto them during initial firing which would have been problematic if left alone, so new NGKs were installed.
Fired up easy, no vibration, and the engine idled down easy into a buttery smooth low idle. Road test was good. Throttle response is nicer with the larger bore. Has better "power" than even before the incident, and seems to breath easier with slightly less restrictive intake, heads and dual exhaust. It runs almost as smooth as the 4.6 in the '97, which is impressive for an old pushrod engine like this.
A big thanks to Brian for his assistance in supplying this project the necessary repair parts!
All that's left is to adjust the TV block slightly (O/D comes on at 50 MPH vs 55 MPH, shifts aren't as firm as I like), re-install the 5.0 plate, and the two front accessory bracket braces.