I have a 65 B1. Its got douglas connectors. Also a big give a way is the passenger side of the bed. The bracket that the fording exhaust pipe bolts to is long on the early, and just a short stub on the late b1 series. Mine however has an early bed side as of two years ago thanks to a Pontiace Vide that did a nose dive into my rear on the freeway.
One thing I have wondered about is the J hooks that supposedly hold the top bows down. My truck does not have them and from what I can tell there is no provision for them.
I also installed a 60amp alternator with that kit into my M37. I have a HMMWV 150 amp one sitting in my garage that will get retrofitted very soon.
On the Diesel in a Mogas tank, well, I had an argument with a fellow SPC back when I worked in the S-6 that HMMWVs ran on Diesel, not gasoline. He was acctually going to fuel up our HMMWV with gasoline. I had to get a SGT to stop him. Some of the people they let in the Guard......