Definitely a V8 in there, most likely a 265 or 283 I'd say.

It does take all kinds.

I should mention, also, that the Alan Jones (Alan was a mover and shaker in the Sydney branch of the AHOC) 100S, which he completed restoring shortly before his unfortunate death about forty years ago, was imported from the US with a Chev V8 installed and an ugly nose grafted onto it.