.068" sounds big for an L6, but it may have a lean metering rod (like .048") in it.
Unlike Holley, the cruising range is determined by both the primary main jet size and the thick (upper) metering rod step, changing either one changes mixture.
Changing only the jet changes both WOT and cruise. Changing only the rod doesn't change WOT because (as edski said) all WOT (thin, lower) steps are .026".
Which is faster at WOT: the .068 or .076"?
