To be honest, and this will sound very stubborn.....But I'm no longer interested in dumping money into this car, due to the fact that it's turned out to be a mediocre platform to start with. I'm just going to fix and then sell it.
I have to spend $1,000 minimum for 3rd and 4th gear (TBK), and all that would do is make it so when you're hammering down in one of those gears, you just moved the stress from the gears to the input and counter shaft, especially due to the larger and more aggressive tooth patterns on the TBK and PAR helical cut gears.
Outlawstar: I think TBK only makes helical cut gears. Helical is actually stronger than spur cut, but helical gears put a high amount of lateral stress on the tranny case and shafts. If you're looking at PAR straight cuts, be prepared to change your gear oil every time you change your oil, and also be prepared to spend a buttload on NEO Synthetic fluid every time you change. PAR is in Australia and shipping is a pain in the nuts, price and time wise. They're also being very rigid on their return policy right now, and offering me no $$ back at all, but instead another counter shaft and ring gear that I don't want / can't use.
PS: Anyone can go to a shop that has CAD / CAM / CNC machinery and have them make you a custom gear set. Your options are not limited to PAR, EMCO, TBK, etc..