Does anyone know if any of the parts from newer B series motors will bolt up to the B21 in a '91 Prelude SI? I know it's the forgotten B series but if a B18C1 or a B16A head would bolt on or to the B21 block that would be pretty original wouldn't you think?

Correct me if im wrong but i didnt think there was a B21. I've heard of the B20A5 out of the prelude tho. If it's a B series, then any B series VTEC head should bolt right up to it.

yeah, I suppose any bseries head should be able to be bolted on to any b series block in theory