Is there an easy way to diagnose if the valves and rings or pistons are faulty?.please see details

I have a 18hp Vanguard V-twin (model#3504477) that is blowing white smoke, looses power, and soaks the air filter with oil. I have replaced the head gaskets, the crank case breather, the plugs, the fuel pump, the air filter and oil. It starts up and idles but oil is still ejecting up the tube from the crankcase breather into the air filter. Is there anything else simple that is causing this problem or is it the rings/piston/valve stems/valve seals?

sometimes those crankcase breathers have two small drain holes in them .The breather must be installed with the drain holes at the lowest position or the breather will fill up with oil and run out of the breather . Been there done that lol