I have a T-5 with .72 5th gear behind a '53 235 with a 4.64 to 1 rear end gears, with 28" tires. I can pull a stump in first gear and drag it down the road at 65 MPH without even knowing that its back there (except for all of the honking and police sirens).
I would like to have 30" tires on it to raise my final speed up to 70 MPH, but .63 is not necessary in my opinion.
With your 4.10 gears and inline 6, you will be very pleased with the .72 rear gears. Those transmissions are much easier to find. Mine came out of an '85 S10 which has a 4 cylinder in it.