Armed with the knowledge that grinding is the accepted pratice to get the larger cam installed, I pulled the rocker box off and set to work. First marking the offending areas (Note: as Mr Fast warned, there were witness marks where the large cam had been rubbing on the floor of the rocker box). So not only would material need to be removed from the vertical ridge to allow the cam to slide thru, but also from the ribbing on the floor;
Removed just enough material to get the job done;
Now the cam fits;
Checking thru two sets of rocker arms, not one of them had the 286 casting number that many say are correct for the larger cam, so will be doing more research before proceeding. Still it was sure nice to see the cam sitting in place!