Just to clarify, "there is no" 318 big block nor wide block. I'm sure "wide block" comes from that the heads make the thing look so big.
In fact if you strip a poly and an LA down it's a bit difficult.....unless you are familiar.....to actually tell the difference in bare blocks
I believe poly pans, timing cover and water pump, and timing chain, and probably oil pump and distributor.....interchange.
The "proper" term for a poly is an "A" block. In fact "LA" means "Light A" engine, as in lightweight, even though there were design changes and different heads.
It sounds like this guy is trying to adapt poly heads to a 360......
