It all looks correct for 1934/35 to me. Very nice. With no pre-war matching numbers, I'm not sure that a replacement engine from the correct year would make a great deal of difference except at the very top end of the market (OHC etc.

The only way to tell for sure would be an enquiry to the NOC or the VMCC.

That's a lovely bike Dave, what a beauty

email (option): horror@blueyonder.co.uk

Very nice indeed, especially because its an OHV. A beautifull engine.