got new toy, feather duster!

Hi, to the best of my knowledge, all 73 and up Disk brake cars got BBP wheels. That means some 7-1/4 axles got BBP lugs. All drum brake cars had small pattern.

You can use the driveshaft from an 8-1/4 donor car as long as it has the same wheelbase as your Duster (108"). Scamps and Darts had longer wheelbases and later Valiants also got longer wheelbases. If you have the shaft with the big yoke on it, it's very easy to have it cut down to proper length.

A disk brake swap is a worthwhile endeavor and then you aren't stuck with small pattern wheels, virtually all of the 8-1/4 axles will be BBP.