I ran a 1987 T5 behind a '69 351W for a couple of years in my '67 coupe. The 2.79 gears gave me rediculous highway mileage.... waaaaaaaaaaaaay more fun then the C4.
It cost me $700 for the tranny, shifter, flywheel, clutch, clutch pedal. I had to get the flywheel resurfaced and balanced...