From what I know, take that what it's worth... should be from the 2658920 head casting number. The 920 obviously the last 3 digits seems to have come from 67 and works with 273 and 318 LA motors. On the other hand for me I have 675 heads which is the 2843675 casting number fitting 318's from 68-74 (my block was replaced with a 1970 318 long before I got it).
