I agree with pigdog, ive never had a problem with them in rally car or boosted a-series

should get the whole lot for under $150
machining the flywheel to flat will give it the best chance also

if you want a better 5-speed go the T50, also use in my rallycar and boosted a-series. they are great for it, Dellow make a bellhousing to vbolt it up, if you have the spare time you could prob save some money. A 63 series 5 speed is the other option, they are obtainable if your willing to pay the $1200 bux asking price, this will also get you a dellow kit and celica box installed though and the replacement boxes are $150-250 after that

button clutch is poo, had one in street car for 6 months and i still stalled it occasionaly, should be able to get that for under 300 if you really want. mine was spring centre but still hated it... other thing is with button clutch it gives you no slip... i hated that, meant you had little control of downshifts and particularly compression lock ups when hooking it into corners. but also at that time the car wasn't boosted but i can imagine they would suck for boosted launches... its good to slip the clutch a bit on a hard launch to build up the boost, so when you dump the clutch you dont eat bags of lag