I have the tko with .82 over drive.It also has the 3.27 first. I was using 3.91 gear and I could 1/4 better using 2nd to leave in due to the first gear was so low,thats with a 28" tire. I swapped to 3.23 and I actually get to use 1st gear for a productive amount of time.
My engine combo is 422 ci small block run 115 in qtr @4500' 98 degree weather. In Sac I ran 117 throw out slav crapped and could not get 2nd,or 3rd gear well. I am getting 400 + or - to the ground. I cruise at 1600 to 1800 in OD @70. Hope this helps some on youre gearing ?

I put my new 383 sbc and tko 500 on the road for the first time last weekend.
Rear is 3.08. Even then, the 3.27 first is very very short. not a bother just cruisin from stop signs, but instant redline and tire smoke if I get into it in first. The 5th gear is pure fantastic. The drop from 4th to 5th is NOT a problem at all, and she tach's 2000 rpm @ 70 mph, smooth and quiet as a church. The closer ratios and taller first on the 600 would probably be better, but even then I'd keep the rear axle fairly low, no higher than a 3.55.

if you're uying a fresh one or find one used, the aftermarket versions of the t56 have a 2.97 first and .82/62 fifth and sixth gear ratios (if i remember the exact numbers)
i run one behind a small block in an s10 (for sale!!) with 3.73's; it's great; pulls 6th gear from 40mph clean.
ratios are well spaced for fun, 5th gear fine all day from 30 up.