All the heads throughout the years will bolt on to any block. The differences are in log volume, valve sizes and combustion chamber size. Bolting an early head on a later short block could result in very high compression and vice versa.
The two heads you mention ('66 vs '67) are likely identical. I believe they will both lack hardened seats which may or not be a problem, but they are the same and will interchange with no issues.
Here is a link to show some different specs that I reference all the time.
http://classicinlines.com/SmallSixSpecs.asp#SSgeneral