Where to find stamped serial number on small cam cummins?!

I just bought a ‘74 Peterbilt from an old timer family friend. The data plate on the timing cover is missing. I took some jasco paint remover to the machined out spot beneath the cylinder head on the driver’s side of the block towards the back of the block (where you would find it on a big cam) and there’s nothing. Does anyone know definitively where I should find the stamped serial number??

I have 29 more days to get this figured out or the state of CA won’t let me register it at all. I’m trying to get a low use (1,000 mile/yr) exemption as I’m a small farmer and won’t need it all the time anyways. I need the engine family number as part of the filing requirements. That number would normally be on the data plate. Supposedly cummins will make you a new data plate for a fee if you can supply the serial number so I’m kinda up a creek if I can’t find the number! Any insights would be appreciated as time is of the essence.

Thanks!

 

The only identifying numbers I did find was the tag on the injection pump, which say the pump is for an NTC335 (small cam)