You may have to start tearing in to it to look for other clues that can be cross referenced. You may be able to google the serial numbers on the carb or distributor. Sometimes, even a rod or main bearing will have a part number or even the "Ford" name, or "Moline" name stamped into it for instance to identify the engine brand, if it's not fully babbited. I'm sure if you found a 1930's parts book, it would reach back that far with part number referencing if you can find an actual brass era parts book.
