In my application, I'm using a 29" tall rear tyre and a 3.5 diff ratio and this calculates out to about 1850 rpm at 100kph (~62mph) which seems a pretty good compromise.
I plan to use a speed based lockup system for the convertor, based on my own design electronic circuit.
A more simple system can be derived by using the 4th gear output signal fro
m the transmission to lock the convertor, with an over ride when the brakes are used. This is a fairly common system used in some aftermarket lockup kits, which only requires a relay and some wiring.
Some other kits sense engine vacuum.
Try these links for some good information:-
http://www.bowtieoverdrives.com/ NEW Aug 2003
The July 2000 issue of American Street Rodder magazine has a very good article on setting up the TV cable.
(See also the /700R4p1.html link above)
I can't vouch for the following information but it might be worth checking out:-
Note: When searching for a 700-R4 for use in a conversion, remove the torque converter, and look on the front plate inside the bell-housing for the casting number. Get one with the last three digits being 732. This ensures a '87 or newer unit with the best of GM's updates.