Going through some parts catalogs for the 62 F100. It is showing three different engine sizes for the I6. O'reillys lists the engine as the 3.7L. Rock Auto gives me the options of the 3.6L and 4.1L. Were there different engine's for these trucks? And how are they figuring these sizes considering that they didn't use "liters" as a measurement system for these trucks in the 60's.