The "milk can" lifter has a mushroom-shaped pushrod seat that projects up into the side cover area, and uses a shorter pushrod. The later engines use a lifter that's a little shorter, and does not have the odd shaped top. Those shorter lifters are available on Ebay pretty often. The amount of wear you've measured is well within the possibility of regrinding, however. The price of both types of lifters has gotten outrageous!

www.ebay.com/itm/256404768741?

Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!