Is there a simple/easy way to ID a 273 engine vs 318?

Just under the front of the drivers side head, there is a flat place on the block right where the head and block meet. Scrape the paint off that pad and you will see a string of numbers. Somewhere in that string of numbers, you will see either 273 or 318. You will probably need a gasket scraper, a small, stiff wire brush and a can of brake cleaner to get it cleaned off to see.