Just a point to clarify......lots of guys are running T5's with a 3.07 R&P.....but they're running the .86 T5 with the 4.03 1st gear, most likely from behind a 4 cylinder S10. A .72 T5 from behind a v6 with the 3.76 1st gear will not work as a 5 speed with a 3.08 R&P and a 28-29" tall rear tire. It'll be great through the first four gears but you'll need to be running like blue blazes to maintain speed in 5th gear. You need to determine WHICH T5 you're buying and this is determined by the tag on the drivers side of the transmission or the bar code sticker. The casting numbers won't help one bit. I've outlined a manual way to spin the transmission to determine the ratio in my webshots "shoebox" album. BTW....I have a nice 3.08 diff as a reminder that a .72 and 3.08 won't work together.
In fact, I would go so far as to recommend a 3.73 coupled with a .72 T5 for max efficiency in the 55-65 cruising range. My .72 T5 with 3.42 R&P runs at 2000 rpms at 70mph and my vacuum comes up higher at between 70-80 mph. I would suggest that the key to maximizing engine efficiency is to gear so that your normal cruise speed is at 2100-2300 rpms. That still gives you plenty of throttle for higher speed cruising should the need arise.
Scott hit the nail on the head with the Hybrid T5 with the S10 tailshaft and shift forks. The ratios are much friendlier and you'll be able to stay right in the center of your 235's torque curve all the way through the gears. I'm building one now for a 40 Street Rod. Driving the 235 with a T5 is just plain FUN!!!!!!
Dave
