Sell your 4 cyl Frontier and buy some plane tickets for Indonesia or Colombia or somewhere besides the USA and go purchase a diesel and have it shipped home.
I just might do that if Mexico sells them. I've looked at them in Bogata, Colombia. Really cool. Made in Japan, I've looked at 6 cylinder intercooler 4x4 for about $35, 000 US dollars. Got the brochures and everything. They even had some Nissan Pathfinders in Diesel. What's up Nissan, bring them here to the USA.
If you want towing capacity buy a Ford powerstroke F250 or F350 before 2003 so you get a 7.3 liter engine or by a GMC or Cheverolet with a Duramax Diesel and Allison Transmission then you can tow anything you want.
Or if you are really cool buy a Ford truck before 1994 and convert it to waste vegetable oil without buying any special expensive kits. Filtering vegetable oil however is a royal pain.