I have a set of 62s I've been saving and have some info on them. Looks like 62s were used on GTOs and Grand Prix and some birds. 400 and 428 higher Hp engines. Also used on auto trans cars in lieu of 48s for standards. Factory shows them at 72cc which if correct (have them cc'd to be exact) puts them at the compression you mentioned. I am presently running 72 cc heads (670s) with flat tops and have found 93 octane is not enough to let me time the engine to run its best. Octane booster has been an easy fix for me.
Bottom line... 62s are desirable performance heads with enough octane.