cam bearing issue

This is a low mileage engine from a 78 motorhome. It was untouched internally until today. The stock motorhome cam is kind of a slug so i wanted to install this hemi grind cam a friend gave me. The untouched motor has about 40 k miles on it. It runs great just kind of a dog. The stock was tight coming out until it cleared the rear bearing. It did turn freely before removing. I do have the stock rv cam, i will try the "shaving" idea. Thanks for the input.