Bob, you get the impression there is a lot of local technical talent... You need to join us this Saturday.
More on the transmissions: Technical specs for the
TKO-500/600 at
http://www.5speedtransmissions.com/tr-3550.html. When you view this site, click on the hot link that compares the Tremec to the Richmond trans. That will answer many of your questions wrt to RE ratios, tire height, and driving habits and preferences.
and the T-56 at
http://www.5speedtransmissions.com/6_speed.html
I am puzzled by your "regearing". The 500 and 600 are available as 0.62, and 0.64/0.82, respectively. The 500 torque spec is <500 ft/lb, whereas the 600 can handle >500 torque. Both are approx $1900 new. The T-600 incremental cost is minimal, approx $75 more. Both are approx 24" long from bell housing to rear spline. if I remember, both weigh about 90lbs
The T-56 is almost 28" long. Gives you 2 OD Gear options you want. It will cost you about $2400-2500. It weighs about 125lbs.
I did not know about Jimi at standard transmission in FW, so I had to learn the hard way. Nothing like trial and error. Learn what you can, and validate with jimi.
See you this Saturday, Francis