26 or 10 spline?
 

When buying a clutch, do I need a 10 spline clutch or 26 spline clutch?
I am assuming 10 spline..

10 if you use the stock transmission

Now my second question is why is there always the option for a 26 spline?

You can purchase and install a 26 spline input shaft for our cars, it is strong than the 10.

Is the input shaft worth buying for my car? or is it for more higher horsepower cars?

the 26 spline is deffinetely worth the money spent in your scenario. Just adds safety and a little xtra piece of mind---espescially if you race on slicks. Ive seen more than few broken trannies(input shaft rung off) on track vehicles with 500+ hp

it's insurance. with the amount of power you're running, you might as well step up while you're replacing it.

I thought about going to a 26spline when I upgraded my clutch. I am in the 450rwhp range, but the car wont see any slicks. Maybe some DR's but my car is 99% street driven so i thought it wasnt worth it.

Plus some day I want to do a TR-6060 conversion when I can get the Viper .50 overdrive gear.

I would say if you track the car alot and run slicks I would defineatly get it, if it is a street car I would say you are fine with the 10 spline.

I would also recommend you go with the Mcleod RST clutch. It is expensive but worth it IMO. I have 2k miles on mine and it is great. Search some for Spec clutches and you will see very different stories.

Good Luck.

++++++111111 on the RST, don't go cheap on the clutch.
I am making 430rwhp and run with DR's at the track all the time, still have the stock input shaft.