chevy engine in a duster ?

Take any tube chassis drag car. What is left of it that is oem? Even the Duster that is on here, sure it is an RB style motor but what on it is from Ma Mopar? Aftermarket block/heads/crank/rods etc. Is it really even a Mopar any more? Besides, racing at that level aint cheap, why make it any worse than it already is?