OE non adjustable rockers? you have that much lash at the rocker on base circle and the lifter cup is up against the retainer clip? Yes you would need longer pushrods to elim that .035 lash at the rocker & additionally to move the cup below the snap ring (for some preload) and iron adjustable rockers MAY be a solution. EDIT what length of pushrods do you have? MORE EDIT hyd-7.510". hyd with adj rockers-7.23". 273 solid lifter pushrods-7.340"