BB and crank arm compatibility
 

hi guy i have to buy an new LH crank arm and i just wanted to know if there was a way i could tell if the arm and bottom bracket would work together? is that all i have to worry about or is there more? would i be better off just buying a new crank set? because the set is brand new it's just that the threading on the arm for the peddal is stripped on the LH side.

As long as your crank doesn't hit the chainstay, the length of the BB for the LH crank is irrelevant as far as I know.