IMHO, the 8-cyl injector harness to get... Cadillac Northstar and Olds Aurora 4.0 V8 around the mid-late 90s (give or take).

The harness contains only the injectors + 1 other sensor, it lays right on top of the intake with no other junk crossing over it, it has a big connector in it that you can use on your car if you want, and it's dog-gone cheap!

Ford 5.0 and 4.6, Magnum V8s and others I've looked at either require fuel rail removal, have injector banks split into 2 harnesses, and/or have a bunch of other sensors and junk in the way.

Steps (as I remember them):
1. remove the engine cover,
2. unclip each connector/injector (this takes a little practice on the metal push-clips),
3. follow the harness under the TB to the top of the transaxle and cut as far on the other side of the main connector as possible (but that's usually only a few inches before it blends into another harness).
4. pull the big connector under the TB, bending some small brackets, etc, to get clearance.

It'll take you about 15 min to get one out if you're slow. I've grabbed a few of these harnesses in the past and often the injectors are gone from these cars already, so there's 2 min saved on the injector clips.