OK, plain and simple, Holleys are NOT designed for off road. 4 wheel and off road did an article on this back in 2001, and they had problems with the same carb setup. I suggest you keep this carb on the street. Edelbrock performer can be set up for off road, and The Rochester carbs are already pre-set on the larger GMCs In the late 70's-early 80s. Heres a link to the on, line article http://www.4wheeloffroad.com/techarticles/11538/ Enjoy!