1952-59 Ford 4 bolt block?

Hey everyone,

I was at a huge boneyard I discovered near me the other day- it was gorgeous here, so I drove the Ford. When I got there, a friendly fellow was commenting on my ride and asked if I had (and please forgive me if this makes no sense-I'm not sure if I knew what he was talking about) the flathead with the "Canadian" or "4 bolt" block? Apparently whatever it is that he was talking about is supposed to be rare and/or sought after.

Any ideas as to what he meant? It's been driving me nuts.

Thx