273 Engine intake upgrade turned sour

It appears the photo at the bottom of post 5 is the camshaft lobe of concern (don't know what "west marks" refers to). No expert, but it doesn't appear like normal wear and perhaps is a void in the original casting. You would think Quality control at the factory would have caught it after machining, but might be the OE camshaft from 1960's before automated video inspection, and Billy-Bob on the inspection line might have been focused on quitting time. If the lifter doesn't touch the void, it might work fine (has for decades?), but appears you want to up-cam regardless.

Your idle sounds fine to me, indeed more stumbly than I prefer, but many here desire a poor idle, like a "race engine", which pours out noxious fumes from excessive intake-exhaust overlap. Owners can legally do that now, but risk public outrage which may limit our classic car hobby, as was done for "rolling coal" in diesels and loud mufflers. I installed a hydraulic RV/Torque camshaft in my 1965 273 with Rhoads leak-down lifters (poor man's VVT), for smoother idle and better mileage. Ball & Cup pushrods for a 1970's 340 T/A fit and the adjustable rockers let me ideally adjust preload on the lifters.