Ball Joint Confusion Help

I currently have a 72 Duster, I ordered and installed a Hotchkiss suspension system TVS for the 68 thru 72.

During the installation the sway bar wouldn't fit. After looking at the engine mounts it was assumed that somebody during it's lifetime had swapped a 73+ front K Member. This would also explain how I had disc brakes that appeared factory. Summit racing immediatley swapped me the sway bar for the 73+ kit, and it installed no problem.

I have an awful vibration at 50mph. The driveline is new since I swapped in a Dana 60 in the rear and the tires didn't have any issues before, however, they have sat for 1.5 years.

Could I have installed a Small Ball Joint Upper A-Arm in a Large Ball Joint Spindle? Is this possible?