what's the max ls6 throttle body size?
 

i need to know the biggest size throttle body that you can get is it 80mm?

You can get a 100mm from sponsors on here. Probably 105+ now.

If you're asking what the biggest size will bolt to a stock intake, the Professional Products 85MM comes with an adapter plate that will let you bolt it on. Thats the biggest one for a stock intake.

anything bigger than stock is a waste since the intake manifold opening is only 75mm