I have a Head(ache)... can you help?

I have a 1968 340 that was stored away, that I am now starting to show an interest in again...

I am looking at that top of one of the heads; the casting numbers that i can see are:

AAWJ 340

2631894 D

03129

Can anyone tell me what I have here?

If this is a "J" head, is it possible that it was factory installed on a 69 Dart?

I havent pulled the head, but I always assumed that it was the bigger valves.

I have only owned 69 and 68 340's...

Thanks!