Technical Will 270 Poly heads fit on a 240 poly

Any early Poly gurus out there? I have a pair of 270 poly heads. I am trying to find out if they will fit a 240 Poly block, without modification.
Any help would be great appreciated.

Vincent

 

1956 Motor's flat rate shows different head gaskets, but that don't mean much ...

 

Yeah, my Hollanders says 56 only but it might be one extra bolt hole or something like that.
Head gaskets may differ due to different size cylinders?