340 cam in a 318

What’s the drop at 10-15 degrees before and after TDC because that’s where they are close.

Plus, whatever the drop is won’t be the same when the valve train is installed. They only way to know for sure what you have is to measure it. Anything else is a guess.

Really? I'm not explaining it..
I will say this, If you know the cam lobe specs and it's timing relationship to where the piston is in the bore, then you can get pretty close. Once you get the cam, then you can do a final measurement .