1st Gen Crew Cab Engine

If intial cost is the biggest factor then buy a Motor Home 440. I voted Cummins before I saw your write up. After reading that and seeing how you wont be using your truck as a daily driver the 440 would be the most economical way to go. You can buy a 40, or 50,000 mile 440 for $450 to $500 give or a take a couple hundred. A couple gaskets and a enigine enamel spray bomb and your ready for a 100,000 miles. Plenty of torque when you need it for towing,hauling.