But oiling and drain back holes are a issue. I dont recall if the oil supply passage is in the same spot on a poly vs la. You would need external oil drain back lines to the oil pan if you wanted poly heads on a la block.
Someone built a odd small block for the Engine Masters Challenge like that. External oil drains, Poly heads on an LA and a cut up LS intake 'cause nothing fits that combo stock. Had to drill a Poly cam for LA rocker oiling too.
