From a post by orange45 thanks George
as mentioned, you really should start with the "auxillary valve body th700" which was produced between 1987 and 1992. these units had all the factory upgrades incorporated in them. some of the tranmission suppliers like to boast about their transmissions having "several HD upgrades". those would be all the factory upgrades........
part of these upgrades are:
a better pump design
better valve body and servo
better input drum
better input shaft ( upgraded from 27 to 30 spline)
accordingly, a better converter ( partially due to the spline count increase)
better rear sprag setup
amongst a few other odds and ends
the "auxillary valve body" actually referrs to a a small auxillary portion of the valve body that bolts to the indise of the trans towards the rear. it supplies much better clutch holding power for fourth gear versus the earlier designs. and it's one crutial upgrade that can not be achieved by "updating" an earlier unit. sure you can put in a shift kit, but you don;t get the same results.
th700s are great transmissions. they got a bum rap because the very early models, 1982-83 had lots of problems when put to severe use. the aux vb units usually go 100k miles in full size trucks. at least that's what we wanted to get out of them when we rebuilt them at the trans shop. and the vast majority of them did. that can not be said for most automatic overdrive transmissions.
if you're going to have on built for your rig, then i would definetly install a MILD shift kit, like the one offered by transgo. do not make it shift too firm or it'll break the aluminum lugs right out of the case. and then you're back to square one.
i would also highly recommend using a kevlar band 9 to cope with the heat and extra load ) as well as an HD sun gear shell, commonly referred to as 'the beast". besides that, get a good quality torque converter with the HD torrington bearing upgrade and kevlar or ceramic lockup-clutch liner. stay away from B&M converters, or it'll be a mistake you won't make twice ( ask me how i know ).
last but not least, find somebody who's well versed in these transmissions and insist on them using high quality components like borg warner or raybestos frictions and oem planets, not the cheap chinese crap......
it'll be money well spent in the long run.
also, make sure you run a quality transmission cooler. use a twisetd fin style, not a tube and fin 9 they're not very efficient at all ).
as far as wiring goes, there are several outfits that can supply you with a 'stand alone" lockup harbess. painless, jags that run, e-z wiring and others are all good.
alright, my 5 minutes are up and i have a two week old that's crying.
best of luck and always remember:
autos rule!