oil coming out the breather is usually alot more mundane than major engine damage. A valve bad would pop thru the carb. piston ring blowby would include smoking out the exhaust.
with the advent of aftermarket rockers and FE oiling mods, chances are there is too much
oil getting into the valve covers via rocker oiling. coupled with a valve cover without a baffle makes for
oil puking out the breather.
do you have factory rockers or aftermarket. solid cam or hydraulic.