After A Long burnout last night (assisted with a 100 shot of NOS) Drivetrain like rumbles in the middle of first, And it may be rougher in other gears, but i cant be sure of that. Anyways im thinking its the tranny since it seems more specific to 1st gear. But i guess it could be the clutch, im not sure. If it is, is there a good Performance Re-build kit, or a place to get good tranny thats already built? any insight would be greatly appreciated.

I have a good used one if you need it. You may have sheared the taper pin in the diff.(very common) I have an extra diff as well.