Is your duster a factory v8 car? If so i have the motor mounts to install a big block without having to change out the k frame. Just removed the 440 from my 71 dart and have no need for them anymore.
Previous owner of my 68 Barracuda modified the original one to take a BB. I don't plan on using it as I have a SB to drop in and a newer spool type K for it. I know it is strong as they used to drag race the car using the BB.