Help with 340 compression + cam change

Yes.... look to find where the valves are .010" from opening or closing to see if the advertised duration works out to what is expected, and measure peak lift too.

And for interest, check at .075"lift . Note those angles on valves for #1 and you can get a fair measurement on ICL (intake center line) to check cam timing. (For cam timing, you normally measure at the lifter body and look for the .050" lift points on both flanks of the intake lobe. Measuring at the valve is less accurate but will give you an estimate of timing.)

Again, make sure the engine has been run to pump up the lifters.

None of this may change anything in your thinking, though the cam timing might be of interest.