The bell housing bolt pattern on a 2.8 is different than the 2.3, the mustang uses a cable operated clutch to the rangers hydraulic operated clutch, the computers are more than likely different
You can swap in the t-5 that's behind the 2.3 (although the shifter would be further back). You would probably have to fab a new trans mount, and have the drive shaft redone.
You could get a aftermarket hydraulic slave cylinder to operate the clutch for the t-5. You would have to adapt the line to the slave cylinder, and fab a bracket for the slave cylinder.
You would be better off switching the computer and it's wiring harness.
Is their any problems with the 2.8 that's in the truck now or is this just an idea your kicking around. I had a pinto with a 2.8 and a 4 speed, ran great and the gas mileage was close to my 88 ranger with the 2.3 and 5 speed. The 2.8's are great engines, stay away from the later 2.9's, 3.0's, etc.