I wouldn't do a cam job, WITHOUT replacing the lifters.
You're correct, Crane tappets are the same thing, and people have used them. The bore is the same. They're (Crane) made by Hylift-Johnson, (Now Topline Automotive Engineering) who used to also make HD's lifters, but no longer do.
The S&S tappets are great, but if you're not going to be redlining/racing the bike, anti-bottoming (Travel Limiters) features are a bit overkill, IMHO. OEMs will work and are fine. S&S tappets would work fine.
“When the going gets weird, the weird turn professional....” ~ Hunter S. Thompson~
R.I.P. Rubberdown. 1971-2012
2005 E.G. Classic
Baisley Oil spring
Rinehart 3.5" pipes
S&S adj pushrods
3 stickers, adding 5 hp each. I swear......