Can i trade in my toyota tacoma for a diesel truck?

I'm sure you can, find a Diesel truck first, then work out a price on a trade. I would sell your truck privately, used Toyotas truck still command a good price. Trading it in, the dealer will lowball you.

Straight trades are not gonna happen unless you trade for a diesel worth a Lot less than your truck. Dealers are there to make money, not swap cars. Any decent diesel truck is going to cost considerably more than your Yota is worth.

Sell the pre runner privately and purchase the diesel truck privately as well. 7.3 ford diesels are strongest and longest lasting but are only available in older trucks.