I just got a 4.6l out of a Mark IIIV it's complete with tranny and wiring with computor. My question is where would I find upgrades like wiring harness, cams, intake, throttle body etc.

Thanks in advance!!

 

Cams, intakes and such should be the same upgrades as an 01 Cobra Mustang, so look for 01 Cobra Mustang upgrades.

 

Where would the most affordable places to look for those parts be?

 

You may want to rethink on the cams. Those are around $700/pr. If you do change them don't go hog wild or you'll be needing to retune. Any way you should get a tuner like an x3cal from SCT to maximize your engine. I've found prices are all about the same on parts from place to place. You can do searching if you want to save $5-10 bucks here and there.