The best you can do is go through the Judging Standards and Plucks's frame evolution study and start to narrow it down based off of a bunch of little things here and there.
http://www.plucks329s.org/frame.htm
Remember that a lot has happened to these cars in the past 90 years and it is very hard to find unmolested examples. I'd guess that the engine is a replacement put in sometime in the car's history. You could try lifting the body to see if a frame number is visible which would give you the original engine number.
-Tim