offenhouser or a airgap?

yes headers
some head work
3speed maunal
i dont know what offenhouser i have.
from others i have talked to i should go with the airgap.
I have a airgap on the 77cj7 304 with a 1" spacer but the jeep has other issues.
any brand timing chains I should use or to stay away from. the chain on the 340 now is sloppy and it is only 20,000 old or so.