The 302 was developed for military use in 51 or 52, but it was introduced in civilian trucks at the same time and was produced through 1959. Both models used the same crank and pistons. The military had provision for a large motor mount in the front part of the engine. The civilian used the same mounts as the 270 of the same year. The military did not have a hole in the block for a fuel pump, but the cam had a lobe for it and a hole can be made using a gasket as a template. The military used an auto trans and had a different starter arrangement. There is a locator boss on a military block that has to be ground off to accommodate a civilian starter. A civilian flywheel housing and 6 bolt flywheel bolt to the military. The military used a sealed 24v ignition system which is usually replaced with a civilian ignition system. The military has a carb with a snorkel to keep water out. This can be removed leaving an intake manifold with a 4 bolt pattern that will accept a WW Stromberg. The 302 was replaced by the V6 family of engines in 1960. The 270 was still built until the early 60's for use in step vans. This was probably done because the step van builders didn't want to re design the dog house to accommodate a V6 and it was probably thought that the 270 was more economical than the 302 in a step van. The 302 is a very stout engine and is capable of putting out a lot more than its factory rated 145 HP. I have been tinkering with them for over 50 years.