Don-
Depending on the cam you are running, you might not want to go with much less than 3.31s. I think the .83 5th with 3.31s is perfect- motor runs right between 2500-2800 (60-80 mph) while cruising on the highway and has plenty of passing power in 5th- you really don't ever need to down shift on the highway to pass- unless of course you want to
With a 2.88 and the .83th, it might drop your rpm too low and out of the powerband and the engine might even lug a little bit- of course this all depends on your cam. (for reference my cam is comp cams 292H. duration @50 is 244/244 and lift is .561)
But even with the 3.31 rear, the 3.27 1st in the TKO II is still very usable for normal street driving. But the 2.87 1st in the TKO 600 would be better.
edit: BTW, Walt did my car. You will be very happy with the paint job. What color did you pick?