Comp Cams makes a stainless heavy duty roller rocker for the Chevy 153/181 and the Chevy six cylinders! 1.75:1 and capable of withstanding anything that the bulky aluminum rockers can tolerate. They will fit under the Mercruiser rocker cover without modification!! Ultra Pro Magnum XD Rocker, part# 1827-12 for the six cylinder.
More than one of my drag and round track friends are swearing by these and they are more mechanically efficient than aluminum too!!
