There may or not be an equivalent ag model, I don't know enough about JD history to tell you if that was a thing in the 70s.
Suggest you go to tractor data for the 302a:
www.tractordata.com
Look at some key specs like made 74-81, 2.7L 53hp 6300lbs with loader for example.
Then look at the ag tractor list and start matching ballpark specs:
www.tractordata.com
Pick out some likely candidates -for example the 1130 is pretty similar
www.tractordata.com
Made 74-79, 2.7L 53hp, 4800 lbs without loader, etc.
From there look at Deere parts catalog diagrams for major assemblies and Google images of both machines to compare.
Another thought is to find part numbers or used assemblies at parts houses and see what other models it fits