There should be a little flat pad just to the rear of the distributor, over the fuel pump. You may have to scrape the slime off to see a number stamped onto this pad. This would be the serial number, in a form such as F0821TA. Those last two letters will tell exactly what the engine is. For example, in '65, TA=230 w/ 3-speed from the C10-20-k10-20 models.
