Same here... the TKX has a similar feel to a T-56 Magnum, with smooth shifts at 7000rpm.

I'm pleased, and do not miss the Muncie transmission at all.

1968 Camaro with a 454ci, 3:55 gears, 26.68 diameter tire (possibly going to a 27.15 in the future)
Right now with the Muncie M-20, I'm turning 3200rpm at 70mph. Staying with the 2.87 fist gear, What OD ratio would you suggest?

If my math is correct;

.81 should put me at 2592 rpm @ 70mph
.68 should put me at 2176 rpm @ 70mph

This is just a cruiser car and I have a lot of long straight roads around me. I do a little auto X and would like to cruise comfortably on the interstates.

Depends on how low of an RPM the car will tolerate.
Cam choice is a big factor.

Can you drive the car smoothly at 2000 rpm in 4th?
What is the lowest it will tolerate?
What speed do you drive the most & how often to you like to shift?

My car has 4.10's & does not like to be under 2000rpm, (it idles at 1300) so I chose the .81 & can now drive it in 5th at most speeds over 45.
It keeps me from shifting constantly, and I did not intend on a long distance highway car though.

Maybe a 6 speed with .80 and .63 would suit me better

That is ideal as long as you are willing to deal with potential floor modifications as the T-56 is much bigger.