Use the specifications for the engine the cam was designed for. The adjustment spec is also the height of the "clearance ramp" built into the cam. so if you go with a different clearance, the transition from clearance to lift doesn't happen at the right time. That's also the reason not to use hydraulic lifters on a solid lift cam, as it increases the total duration by a bunch. Hydraulic cam clearance ramps are usually only .002" or so, instead of .015" or more.
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!