Chances are that you'll botch a few lifter feet when doing the lash machining. Invest in some extras to avoid any down time.
Foot measurement is 14.50 or 17.50mm to work with standard-length valves. Valve/cam lash adjustment is done by machining the base to the desired clearance. Pick which ever length is closer to (but not under) this required "shim" amount.
These customizable two-piece cam lifters are designed for both long-term economy and ease of set up. Combine with a solid lifter racing cam and get the revs boiling!