Here we go again. The OP has stated he's buying a Ford but of course the Ram boys gets their shorts in a knot that someone else ( and there are many) has decided on a Ford.
Also funny that someone thinks an Aisin transmission is "American". I'd be surprised to see how many parts of it are actually manufactured in the US, considering the vast majority of their plants are in Asia.
I guess if the Japanese transmission is assembled in the US then that must make it a US product?
So using that same logic, if a truck is assembled in Mexico......?
To respond to the OP, go for the diesel since you will be full timing. Good luck with your venture. Enjoy.