My disc brake conversion on my 65 was courtesy of OEM parts. I swapped in spindles from an 84 C10. Converted the truck to 5 hole wheels. A true bolt in project. I had to change the ball joints, brake hoses and tie rod ends. All OE parts. Sorry yours was not as easy.
Measure your spacing: both back space and distance from hub center to outside of caliper. Take that measurement with you to the junkyard and find a set of rims that work. The problem may lie with the shape of the inner part of the rim and the way it comes down from the bead. Other rims of this vintage may not have as deep of a droop.
