On my 213s, which are I believe 1973s, after hot tanking it was easy to see rings of discoloration around the valve seats. But your heads are earlier and I'll bet no hardening of seat areas was done.

From 346 through 452, the ports are all the same, according to many who have worked on them. Find Steve Dulcich's three part article on bigblock Mopar heads, it is pretty definitive.

R.