Disc question
First of all, they didn't make a 10 X 1.75 front hub and drum assembly, but that's beside the point of this discussion.
Sorry, I know this and just typed the dimensions for the rear drum because it comes up more often. I fixed it to read 10x2.25" like it should have been.
As I've mentioned before, there are no before and after dates in any factory manual showing different drum brake spindles used in a '73 A-body. So, only one spindle (3402739) means only one ball joint and one set of bearings. The '71-2 9" front hub and drum is a 3580702 made by Budd and uses the small bearings (A1 and A4). the '73 9" hub and drum is a 33699574 and uses the big bearings (A2 and A17). I know this form owning two of those early '73 A-bodies with 9" front brakes. At the time I parted them out (both rubber floor mat cars with totally rusted out floors) 35 +- years ago, they were both virgins. Nothing had been messed with. At that time, there were still quite a few of them running around here as daily drivers, and those front hub and drum assemblies were gold, as most people weren't looking to convert those cars to disc at that time. Those drums were the first thing sold off those cars. It was a surprise to me when I first encountered them too. After all my research, I discovered how unique they were and that even though they were 9' brakes, all the other attaching parts were the same as the 10" drum and disc brakes. That came in handy when I sold a later disc brake setup off say a '73-4 E-body or later F body to someone putting them in an A-body and needed the upper control arms. The service bulletin I've seen posted only mentions going from 9" to 10" in December, not that they changed from the '72 and earlier parts to '73-up parts. It wouldn't be the first time that Mopar designed and made a part only to change their mind and make something different a short time later. A case in point is the early vs late '66 Barracuda grille emblem. They tooled up to make a V emblem to fit the new grille that year only to decide a couple of months later to make the fish version. There are other examples, but, this diatribe is getting long enough. In closing, just look at all the factory '73 manuals and even aftermarket ones for bearings and ball joints. You will see only one listing for both on a '73 model.
Quite frankly, I'm tired of this. There are enough errors in the parts manuals and discrepancies from production (especially early production for a given model year) that they don't prove much of anything when it comes to special cases.
The '73 parts manual shows NO 10x2.25" drums or hubs at all. It does have a part number for your magical 9x2.5" drums that use large bearings. But there are a handful of other members that claim their early production year '73's still had small upper ball joints.
So who to believe? Beats me. By your account all drum equipped '73's before 11/1/72 (per the TSB) would
have to be 9" drum cars, because there is no part number listed for a 10x2.25" drum/hub with large bearings. So no 10" drum '73's before November (ish) per the TSB if that's true. And of course, never a small upper ball joint UCA.
And of course that makes all the other members that have claimed in the past that their early model year drum brake '73's had small upper ball joints are wrong. Truly, I have no reason to believe them or you, since either could easily be misremembering something that happened decades ago.
With Ma Mopars history of reusing parts, well, it could be anything. Because I wouldn't bet a penny that small ball joint spindles and UCA's
never left the factory on a model year '73 car.
Bottom line is, check which ball joints you have before you do a disk brake swap so you know if you need new UCA's. Goes for everybody really, because you can find just about anything on a 50+ year old car and just because it's really old doesn't mean it's original.
As for the magical 9x2.5" drum hubs with large bearings, well, I'll believe it when I
SEE it. Not before.