Do you have an idea of the year of the truck? The tall side cover would indicate it's either a 216 or an early 235. They're both splash-oiler Babbit-rod engines, and that one looks too far gone to restore. The 216's date back to 1937 or so, through 1952 or 53, and the 235 started out in 1941, I believe, and also went to 52 or 53 before it got upgraded to full-pressure oiling and a different cylinder head/short side cover. According to a couple of websites I've found, it's supposed to have a 216 engine:
http://www.autogallery.org.ru/m/cmp15.htmJerry