Kind of slapped together
Join Date: Jan 2010
Location: Bossier City, LA
You'll need a 1991-1993 5.0HO MN12 for donor to make it easy, might as well use that motor (the 97-93 Mustang 5.0HO won't quite fit, but the 94-95 does, because it's the same motor)
Well, the MOTOR fits, but the intake and the accessories don't quite fit the hood line.
From what I understand (please correct me if I'm wrong, people!) the 3.8 doesn't use the same bolt pattern for the bellhousing the 5.0 does, so you'll need a 5.0 AOD also. However, the Mustang tailshaft is a different length, so to use that, you'd either have to have it modded to fit, or use a custom made driveshaft. Again, using a MN12 5.0HO donor, that's taken care of.
Using the donor, you could use the donor wiring and computer.
Do remember the 1990 didn't have the 5.0HO available, so it won't quite be factory no matter what you do.
As to the exhaust - the're the same from after the third cat (one part number in the Walker book for the Y pipe back for dual mufflers), so that's not a big deal. Again, with a MN12 donor, you can use its front pipes. As far as true duals, check MandrelExhaustSystems.COM for their offerings.