A taller FIRST gear ratio would be nice!! The typical TKO500 and T5's come with something like a 3.27 1st. An ultra low, stump pulling, tire smoking, all but worthless ratio (perfect for small blocks,,,,
).
The TKO600 is much better at 2.87, but still, not tall enough for my taste. A 2.78 ratio like the top loader wide ratio trans has would be ideal. I like the .8 OD just fine for my cam profile (2,000 rpm or higher) and rear gear ratio (3.31) that I'm running. .6 would certainly be to tall, unless I was looking for a speeding ticket.
I like to target my cruise rpm for between 70 and 75 mph to match the cam profile, tire size, gear ratio's, etc.