ID these heads?

694spd said

Update:
3418915 castings were 71-72 340-360 1.88 J heads
3462598 castings were the 340 T/A heads

Click to expand...

Not just J. I have a 3418915 "Z" & "O" head.

Was there more than one casting # for T/A heads because all I have ever seen was that T/A heads are 915 heads with offset pushrod holes? Never heard of a 598 T/A head.