Brian, you missed a decimal point there. The timing figures for degreeing the cam are given at a valve lift of .050", because
it's difficult to see the beginning of the lift just a few thousandths off the clearance ramps. Total duration on the 268H will be 268 degrees, intake and exhaust, with a lift of about .450", IIRC. A .500" lift is too much, unless you plan to check the piston/valve clearance very closely.
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!