Rat Rod Girl,
Here are a few serial numbers by year that might help ID your motor:
1934 - Master & Truck (No prefix letter), Standard ("M" prefix) s/n start at 3964078 thru 4708994.
1935 Master (No prefix letter), Standard ("M" prefix), Commercial ("K" prefix) and Truck ("T" prefix) s/n start at 4708995 thru 5500178. Starting in 1935 there was an "ecomomy" engine available and they had a "V" prefix added to the above codes (VM, VK, VT etc.).
Block Casting Numbers by year:
1934 (All except Standard) 837231
1934 Standard 473741
1935 All 837591
1936 All 836010
Hope this helps...
Mike B
