235's went from a shim-adjusted main bearing to a precision-clearance type somewhere in the mid-1950's. They also changed the anti-rotation system from a dowel pin in the back of the upper bearing to a tab at the parting line when they eliminated the shim adjustments. My Federal-Mogul master bearing catalog breaks down the exact change dates, but if your engine has anti-rotate tabs at the block/cap parting line it doesn't use shims.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!