They were used in the bigger GMC Road trucks, firetrucks, etc. The motor in the stand was set up to power farm irrigation wells here in the plains. They are 2 351 v-6's on one block, shaft, and cam. They would run for years on irrigation wells. Fuel hogs, tho.
visit
www.6066GMCguy.org It tells alot more about the engines. Give specs, weight, and all. That will explain the need for 1ton chassis.
My purpose is not for a hotrod, hope to gear it for not more than 70+-mph. Just want to let people see the old beast in running condition. The truck won't have any real useful purpose. 3-5mpg about all it will get.
Cayoterun