Comp Cam XE274H

The XE-HL will out perform the old XE274
so will the Lunati Voodoo if the 274 is not the right (also check pricing) duration (rev range) for your use or compression (converter-gears etc)
stock rockers will work better with lash caps
use Magnum lifters and oil the pushrod ends with hollow pushrods-- do this with aftermarket rockers Iron OR roller
also do the rocker arm geometry drill as well as degreeing in the cam
the rockers could have failed if not installed (mid lift geometry)
roller rockers will require raising the shafts to be correct and stock rockers may also (but much less) with that valve lift
do the work- get the results
start a new thread on your build
did you say what heads you are using
The HL cam will utilize some porting or aftermarket head
the older lower lift cam did not need porting and with no porting did not need more lift