just ordered my frt disc brakes

The thing I like best about my ignorance is that it is so easily countered by simply getting the facts from the folks who know. That said, one of the articles I read about converting early A body fronts to disk brakes, using junkyard MOPAR parts, the author said he wouldn,t use the 9" spindles and ball joints on anything he wasn't pushing around his yard by hand. That guy presented himself as being knowledgable, so I had crossed the idea of keeping the 9" stuff on my '63 Dart coupe. Then I say the Scarebird stuff being talked about, and keeping the 9" stuff came up again. So, just how much smaller and weaker _are_ the 9" spindles and their small ball joints, as opposed to the later A body parts everyone I saw was pushing before Scarebird came along?