Roller rockers with conventional poly locks usually won't fit under stock covers and man tall covers won't work unless you relocate the alternator.
There are some vendors with sell polylocks which may fit under stock height covers. I think Crane, ARP or both may offer them.
Or you may have to find a different set of covers which are somewhat higher than stock but not high enough to interfere with the alternator.
On my BBC, I have Crane Gold Race Rockers and ARP polylocks under an old set of B&B polished aluminum covers. They are just a bit higher than stock but clear the alternator in the front and the brake booster in the rear.
