I had the same problem with my 2.6 powered D50. Whenever I hooked up my utility trailer and went to get wood I ended up in 3rd gear at 45 MPH to make it up hills. I got tired of being passed by Volkswagon vans so I swapped in a 350 small block. World of difference. There is no substitute for cubic inches. Now I just step on the gas and it can maintain 70 MPH loaded with wood and towing my trailer loaded with wood.