You'd better sell the whole thing as a project then start a swap you're not really interested in. If you decide to sell the thing halfway, you'll take the bite, moneywise. because nobody likes to "continue" the work of someone else, well, i don't.
part your engine, or sell as a combo, the choice is yours, then start looking around for a nice full size you really want. Then upgrade what you want on your truck as you go.
to give you an idea, my ranger will cost me close to 4k$ when i'll be done with it. No way i'm selling it, if i were you, i wouldnt go through all that's involved swaping your truck to diesel if it's for selling it.
My old dad always says: Only crazy people never change their minds.
and if you have to, now is the best time
my 0.2 cents