Question About J Heads

I just picked up a bare set of J heads with casting numbers of 3671587.

I've de-coded them and found that these heads could be from the following:

1973, 340
1973-74, 360
1976, 360

My questions are, how can I tell which ones I have, and does it make a difference?

All 3 show 1.88-1.60 valves, but I'm not sure if the chambers or ports are different.

Any help would be appreciated.

Author: admin