Buick 215

My bad I've got some wrong info above. The 300 engine is a 64 Buick engine that is cast iron block and aluminum head engine. Same basic design as the 215 Buick. The Olds version of the 215 had 6 bolt holes per cylinder, the Buick version only had 5. The 300 Buick went to 4 bolts per cylinder. I have read some articles that said the English 215 had 4 bolts but I have a block which I pulled out of a nearly new Rover which has the 5 bolt configuration. Maybe I have it straight now.