I have an LS motor and i am getting a new crank for a motor that i am building for boost anyway the site i am getting it from has 89mm, 92mm, and 95mm what is the difference for boost heads.

 

89mm cranks are straight drop in with stock length rods. 92+mm cranks require custom rods or pistons and a competant engine builder to check clearances. if you're not building a drag engine, stick with the stock stroke.

 

89 is the stock LS/B20 stroke and are perfectly fine for turbo aps. Higher strokes are usually for NA apps.