A generic (sort of) Cummins Big Cam question

FFC Block, no Jake brake

 

Yup that's a compression release on the upper front left alright.
The thing that has me Little confused is the intake manifold.
My small cam 350 had a two piece rectangular box manifold held together with multiple bolts.
Your intake looks like the one on my 1973 335 Cummins.

 

I suppose that could be a 250 Cummins ?
I thought all the 250s were naturally aspirated though....,

 

FFC block has all of the engine oil filtered before being fed to the engine. The earlier NTC block did not.

 

No, the 250 was naturally aspirated ( no turbo) in an NTC block.
From the picture I can see that an after cooler would be needed to uprate to 350 HP.

 

Yea my 350 had the after cooler on it but the 335 did not.

 

They may well have hooked the compression release to the former emergency shut down cable on the Detroit, that closed the flap to the blower.