My experience with u-joints for the older stuff has been that the local store probably has them, but often you need to do one of two things:
- If it is a relatively young person, make him take them off the
shelf and match yours OR, if you get permission, do it yourself
- Find an experienced (not necessarily old) person, they often can
recite the part number from memory
It's as Tim said, good perseverance.
don