4.10s with a th350 will be just about bearable on a highway if you drive at 70 ish. I used 4.10's with a 700 box and 35's. In O/D my speedo reads 70mph when I'm actually doing 65 so the gearing kind of worked out the same , but even with 5 mph out on the speedo I notive the higher rpm, and that's with a lock up converter. If I didn't have to drive it on the road any distance to wheel I would definatly go with 4.88. But remember, there's a big difference between your 1:1 top gear and my .73:1 with lock up!
So if you like your fillings IN your teeth......go with 4.10s!