72 Polara front disc calipers?

[volaredon]

There were 3 different. Upper ball joints among RWD Chrysler products.
They differed among the outer diameters of the threaded shell that held them in. That doesn't mean the machined taper portion that matches the machined taper in a given spindle changed. That I can't vouch for.
Same argument about the style of lower ball joints in 65-73 c bodies vs newer c bodies. So something like a Cordoba spindle maybe fine. The other place they may have differed is the height of the spindle.

I know that among other mopars people have been mixing and matching spindles to get the brakes they want and sometimes ride height differences for years without issue.
I know that is especially the case with A bodies between 9" drums, 10" drums and disc brakes. And the later a body, b body, f body etc swapping to the "big" (police, towing, HD) caliper brackets so that bigger "stock"rotors can also get swapped.

If I was in a bind and had to look for different brake stuff to swap into a 65-73 c body, the 1st place I'd try (yeah I know that lower control arms would have to swap too) would be off a 74-78 c body.
I know that rotors, calipers were the same between these and 2wd trucks and vans til 84, since 2wd trucks went to the bigger lug pattern starting in 85.

 

[Just Carbs]

fury fan.

It would appear that RA is selling a lot of BJs that don't fit a lot of cars.

He didn't say anything about BJs, but he's a brake and suspension man, nothing else. So, there's no telling what he had handy to play with. He did say he had to go with everything from the Cordoba. But didn't mess with the control arms.

From your experience it looks like the late December 76 Cordoba spindles I put on my 64 New Yorker use a different UBJ than the 72 C. Even though RA say otherwise. Or, possibly you have a different Napa UBJ than you think you have. Not likely. Would you be surprised to know that the new radiator Napa sold me for my 72 NY that came out of a box marked for the NY was for a 78 Grand Marquis?

On my 87 Fifth Ave the LB mount and steering arm are part of the same piece that's bolted to the spindle. The 5th Ave and Cordoba use the same spindle "after" late 76.

I'm glad my 72 NY calipers are working good and apparently rebuildable with the available new pistons.

 

[volaredon]

I too came up as a brake, suspension and alignment guy but have messed with Chrysler product ever since I knew the difference between a 1/2 and a 9/16 box wrench

 

[Just Carbs]

He a competent general tech but that's not what he makes his money at.

 

[fury fan]

There were 3 different. Upper ball joints among RWD Chrysler products.
They differed among the outer diameters of the threaded shell that held them in. That doesn't mean the machined taper portion that matches the machined taper in a given spindle changed. That I can't vouch for.
...

If I was in a bind and had to look for different brake stuff to swap into a 65-73 c body, the 1st place I'd try (yeah I know that lower control arms would have to swap too) would be off a 74-78 c body.
I know that rotors, calipers were the same between these and 2wd trucks and vans til 84, since 2wd trucks went to the bigger lug pattern starting in 85.

Some editing was needed in here:
I remember some musclecar guys were looking at using C-spindles some years ago, and IIRC they identified that the taper and/or diameter of some BJ stems is different.
I don't remember what, but remember that taper-drilling of spindles was required. (maybe it was to install a C-body LBJ in something else?)
But re-reading something today, a guy said the E-body and C-body UBJ was the same.
And I found a NAPA interchange list showing the 260-1042 UBJ (that I have in the basement) is for B-C-E-bodies and 73-newer A-bodies.
So I hafta eat crow on that. My world has been overturned on what I thought I knew.
But I also remember guys needing to buy a larger size socket for installing the C-body UBJ, so what's that about?

^ The above was edited from earlier today...

Below is unchanged.
Fortunately, finding caliper cores and rebuilding them is still somewhat easy. While we can't get them at the parts store any longer, used ones are still out there.
When I learned calipers went AWOL I panicked and called Murray Park, 4 used calipers were on my doorstep a few days later, and rebuild parts from RA within the week.

At some point we will need some other donor. I'm suspecting the GM calipers that are popular in the aftermarket conversion kits will be our best bet.
The pictures suggest they are always mounted with a flat drilled/tapped plate with no extra geometry added.
Or maybe a modern caliper with bracket, RA shows lots of modern brackets for ~$25 each.
We will then need 2 plate designs, 1 for drum spindle and the other for discs.

The trick will be finding one that can be readily adapted to the spindle (i.e. with a simple flat plate), and hitting the rotor at the right diameter and in/outboard location.
And the rotor thickness, too. But I think anything that fits a ~1.18" rotor will work on our 1.25".
Brake hose adaptation should be relatively simple, either with adapter fittings at the caliper, or by custom hoses from The Right Stuff or another brake tubing vendor.

But I digress. None of that is the solution for the OP.