The T5 doesn't go into a C4 real easy and it's not robust enough, if you plan any engine modifications. In fact, the older T5s are marginal for a stock 350 in a C5.
The ZF six-speed can be retrofitted to the pre-89 C4s but it's somewhat expensive.
A good choice is the Richmond six-speed. In fact, Richmond sells a special "kit" for upgrading 84-88 C4 manuals with its six-speed that is said to include everything you need for a bolt-in swap for the car's existing Doug Nash
If the car is paid for, you can always take a low interest title loan at the bank to cover the swap. Nice part about that is you are investing right back into the car, it is a secrured loan with set payments, and it is part of making an overall improvement to the whole package.
I don't know if you guys know Mel Foye over at ChevyTalk, (I know him from Corvette gatherings here in SoCal in the past), but he said that he's had problems with the Richmond six-speed in his '62 Vette (Ya can't miss it -- everything on that car except the seats and tires, is YELLOW!). :L He has had it pop out of gear, says it's hard to shift, etc..
I was gonna go that route, but I think I'll stick (NPI) with the DN 4+3. :gap
There is a 1986 4+3 transmission for sale on ebay (#597113141). It looks like the overdrive unit is with it. You can buy it now for $570. or bid on it. Seller is located in Acworth, GA.
You're right Keith, that is (or will be ) a very nice looking ride! Custom paint, eh? Looks good!!
Too bad about the Doug Nash. I just may re-think my position in regards to swapping the DN 4+3 for a Richmond 6-speed, or some other trans.
I'm pondering that, because mine is acting stranger than ever. :crazy
I just got back from cruising the canyons around LA (from here at the beach to out in Simi Valley) and the thing functioned, for the most part, as it was designed to work. Even as I was going uphill through the canyons in second and third gear!
If I would kick the throttle past 60% depressed (or whatever it is - I forget), it would kick out of OD as designed and when I returned to normal cruising, and re-set the button, it engaged just as it is supposed to engage. ad