The bearing conversion is such an expense that the person who had it done would certainly pass on to subsequent buyers that it had been done to the bike.
Some shops stamp engines that they've overhauled or modified; I stamp "BAB" on the large pad below the timing cover on Commandos I've overhauled.
author "Old Bikes"
too many bikes to list, including:
JPN, 952 Prototype, MkIII Interstate, Combat Dunstall, VR880 SS, Triton