you may have some angle milled heads on there, also could be reason not mating up, if so you'll have to get the intake angle milled the same angle.
Also I would highly recomend a solid roller if your not already using one, like stated above flat tappet cams can be a nightmare to get broke in if ever it seems. If your dead set on using a flat tappet, make dam sure you give it a liberally coating of quality break in lube, add a can stp oil treatment with your oil and use a oil very high in zinc and other antiwear additives, like rotella t or devcon, brad penn etc, etc etc.
Goodluck, Charles