70-72 valiant lower ball joints

The lower ball joints are different between disc and drum. Some listings call out that difference, some don't- and that's where you run into trouble.
Take this listing from Rock Auto for instance, some are called out as disc or drum, others are not. Stick with the ones that specify.
1971 PLYMOUTH VALIANT 5.2L 318cid V8 Ball Joint | RockAuto