for gen 2:
they either come with a 3.5 for 500 hp kit
or 3.25 for 550 hp kit

 

my 550 hp. frpp whipple H.O. kit part #M6066-M11P7 and it came with 3.375 pulley. 550 h.p. with 15% drivetrain loss=469 rwhp. i will try and post my dyno sheets! i lost alot of low end torque due to the 1 3/4" LT and 3" h pipe.

 

here are my sheets. hope you can read this!!