JDMedic, Hotrod Lincoln is right. Towing requires torque. Here is my experience with small block engines of the same family but different sizes. I have a '71 dodge van that I bought new and use to tow a small travel trailer. It came with a 318 cid small block Mopar engine that I optimized for towing and added a New Process 4-speed Camper Special pickup transmission with gear ratios 4.56, 2.20, 1.31 and 1:1 with a 3.55 rear axle ratio.
When I installed a 360 cid engine with everything the same except the jets in the Thermoquad carb, the longer stroke engine was so much more torquey that the 3.55 gear was unnecessary and I put a 3.21 rear axle under it.
Now there is no measurable change in fuel economy from the 318, there is less gear shifting required, particularly with a head wind or in the Rocky Mountains of Wyoming where I go every summer for fishing up to elevations of almost 11,000 feet (Beartooth Pass), and there is less interior noise because of the lower RPM with the numerically lower gear ratio.
I hope this information helps.
