Unless your local crank grinder is inexpensive, just buy a Molnar 3.915" crank instead of putzing with a factory 3.75" crank. I'm just finishing doing that, and I should have bought the Molnar. Or whatever your favorite brand is, but I'm suggesting Molnar. Although the new lightweight option 4.25" cranks from 440 source might be worth checking out if you're upgrading heads. S/F....Ken M