I would assume there's going to be a slight difference in length going from an SROD to a T-5 --with the T-5 being slightly longer, since you would be going from a 4-spd to a 5-speed transmission.

The T-5 was first put in the Mustangs around 1983. The World Class T-5 was introduced in 1985 but the more improved versions were from 1990-1995 although, '94/'95 models will be slightly longer than the previous models (deeper bellhousing).

A regular 5.0L Mustang GT T-5 will have a 3.35:1 1st gear ratio and a .68:1 overdrive ratio. The '93 Cobra/Z-spec T-5 will have a 2.95:1 1st gear ratio and a .62:1 overdrive ratio.

 

RUG SR-OD Single Rail 4 Speed Overdrive:

1977/79 Granada 250/302; 1979/83 Mustang/Capri 200 I-6/2.8L V6/302

1978/83 E100/250 300/302/351W; 1978/83 F100/150 2WD 300/302

 

 

Pick a T5 out of a fox chassis Mustang. 1983-1993. Later ones better than the earlier ones. In 1983 Ford put both the 4 speed SROD and the 5 speed T5 trannies in Mustangs. Both trannies took the same part number of driveshaft yoke. But the complete driveshaft part numbers were different. This leads me to believe the two driveshafts were different lengths. I can't tell how much however.

 

From googling, it looks like the T-5 is longer than the SROD, as Jeff alluded to. It also appears that the T-5 requires a different bell housing. IIRC Mustang bell housings use a cable clutch which won't work with your mechanical clutch. Contact the T-5 experts at Modern Drivelines and ask these questions.