Engine size, casting date and casting number are on the sides of the engine block. I forgot what side has what on it. Might need to crawl underneath with a flashlight.
If it is a 318, a single plane isn't a good choice, particularly on the street, or even if it is a 360. 360 heads could also reduce 318 compression because 360 combustion chambers are bigger than in a 318 head. But we don't know what all has actually been done to it.