You might want to consider an E.J.Whitney alternator.
https://www.ejwhitneyco.com/automotive.html
I installed his 6V positive ground unit in the tonner. He uses the front and back of your core and the guts of a tractor alternator tucked inside a housing of his own design. It is a single wire alternator that uses the GEN BAT wire in the OEM harness. It looks like the Ford OEM generator.