Don,

My 93 Vette had 2.73'3 (w/ a 700/R4 & 300 HP LT-1)), and I ran all day at about 1850 rpm at 70 mph. I got 29 mpg on my first trip with it. I didn't like the lack of balls on the low end, so I changed out to 3.55's. My mileage on the road is still about 24, and 19 in town. With the lock-up, the trans run very cool.

I'm setting up my '34 with 3.73's and a R4 from Bowtie Overdrives. I spent several hours on the phone with the owner, and he knows more about OD transmissions than anyone I ever met. His transmissions are all run in a mule before he ships them out. He also (for a small price) sends a pressure and temp gauge with the transmission, and guides you through the installation.

After driving a Vette for 8 years, I wouldn't want a manual valve body either. The stock setup works just fine. You can downshift or hold it in gear as you wish.