Truck towing question

I do expect awful mileage, That, and I know Cummins tows over 10k without breakin a sweat

In fact, you should consider a first gen 12 valve Cummins Diesel . Mine is 2wd A/T and gets 22mpg and around 18 towing. Can tow 10K with it. The late 80's - early 90's body style is pretty cool too. I just did a minor restification to mine.