you really need adjustable rockers for any cam that's higher than stock lift. with stock rocker arms, the higher the lift of the cam, the deeper you sinking the pushrod into the lifter. go high enough with with the cam and you'll bottom out the lifter. adjustable rockers will allow you to compensate for this problem.

the very first 440 i ever built was with a .509 purple cam and stock rockers. I didn't know any better at the time. within 100 miles, wound up wiping the cam and all the metal destroyed the engine. costly lesson.