Gumtree Farm

Hi everyone, I'm new here and hoping to get some help and advice from all you clever peeps. I am the proud owner of a 1977 JF45. She had a heart transplant and is currently running a 351 Cleveland V8 and man is she thirsty!!! I'm looking at a diesel options and was hoping to get your advice on which way to go. She still has the original 4sp box.