If you are looking at less than 500 fwhp then an 80mm MAF will do the job especially in a boosted application. They came stock 1996-2004 GT's and the only difference that I know of is the IAC is built into the late 2001 -2004 units. Couple of threads on the Corral that I started when I swapped the Coupe over to the 80mm.
You can buy an 80mm MAF off of car-part.com. On "Select Part" use "Air Flow Meter" out of the drop down. You are looking for one with a 4.6L motor.
Differences between them:
This one as the wiring from a four wire to a six wire MAF:
You will need this adapter or one like it as the inlet side on the MAF is a square flange:
Light weight billet aluminum CNC machined mass air filter adapter which directly bolts to many Ford OEM mass air systems, such as Cobra, Lightning, Ranger and other Ford
accufabracing.com
I opted for a metal adapter so I did not have to worry about cracking a plastic one when tightening the clamp on the silicone coupler.