68-69 should have a p/n or casting # of 2531914 or 2531915
70 would be 3512847/3512848
71 (spread bore) is 3512099/3512100
72 is 3671878
hope this helps.
I'm looking at the square bore for a 71 340 which is in my dart
the spread bore is to go on my 78 LRT
Your bottom line???