Flat cams in 305's, how about 350's? I worked as a mechanic in a school bus garage for a time when construction was slow in this area.The company got about 25 brand new 1980 one ton dualy van school bus conversions,all 350 powered.Before 10,000 miles,half of them had wiped out cams using the 10/30 fleet oil that previously caused no problems in earlier 350 powered small buses.One bus actually threw a rod on the first school run it ever did.GM tried to ignore the problem,but for sure it was a cam quality problem.
This school bus contractor company wouldn't buy full size Chevy 350 powered buses cause of cam problems in the past from heavy duty use.
From what I heard from mechanics,Chevy small blocks often had cam failures when in heavy trucks.