Andrewtech Automotive offers PPG gearsets in both straight cut and helical cut which you can mix and match. PPG gears are indestructable. A popular route is 1-2 straigtcut and 3-4 helical while maintaing the stock 5th. He also sells RA gearsets if you're on a budget and won't be going crazy with the power mods. Most people choose upgraded synchro's for daily drivers but dog egagement is also available.
Of course I don't know jack about GC's so this could be totally useless info, but I'd give him a call if I were you.