I've brushed and scraped all about the top and rear of the left brake housing and cannot find any numbers. Even the machined flat surface between the brake spring and brake adjust nut does not exist.
Would you happen to know whether engines were installed sequentially according to SN. The difference between your engine SN and mine is 47,441. If I subtract that from your tractor SN I get 18959, which would make it a '49.
I think I have enough info now to order some gaskets.
Best regards, Dennis