For the racer that is running a flat cover on their Donovan SBC engine RBS carries this handy cam thrust shim kit that allows the racer to set up the shims between the cam and the bronze cam thrust button setting camshaft end play up against the steel bushing that is pressed into the #370-0097D cam cover.
Bronze bushing registers in the center of the SBC cam hub and is .810" O.D., then steps down to .680". End to end bronze bushing is .675" overall length and includes eight heat-treated ground thrust shims that are .005", 010" and .020" thick. There are one .005" six .010" and one .020" shims in each kit to set cam end play.