I am looking for a used towing/pickup type truck that will tow up to 4000 lbs, with the best reliability and milage I can find. Also, it needs to have an extra cab space for groceries and suitcase type items as my wife travels about 3 hrs round trip once a week.
Suggestions
I’m kinda partial to the Nissan or Toyota pickups. Their larger pickups are Class III rated (5000lbs). So you won’t have a problem towing. They are also very very reliable vehicles.
You won’t need a full-sized pickup for what you’ve described. I’m rather fond of my '99 Dodge Dakota with the extended cab, and it was rather inexpensive when I bought it last summer. The Ford Ranger might work for you. A Toyota Tacoma or Nissan Frontier would also be good (check the towing capacities, though), but you’ll pay more them.
The reports on the Chevy Colorado/GMC Canyon twins aren’t very encouraging, so it might be best to avoid them.
An Explorer Sport Trac, v8 or v6, should fit your bill. It’s a mid sized 4 door pickup(basically an Explorer SUV with the back turned into a truck bed), the v6 is rated for just under 5100lbs and the v8 is rated for 7000lbs towing capacity with 4wd. Both get about the same gas mileage, 13/19 city/highway.