I would try Randy's Ring & Pinion www.ringpinion.com

You definitely don't want to go swapping caps.  It would be like swapping caps on connecting rods.  The bore is honed after the case is made, so the caps go in their respective locations only.  I'm not necessarily doubting what Greg B's saying, but thinking of how these things were machined I don't see how the spanner nuts are made to the case.  They can't be machined together, so the spanners were made and threaded, and their bores were threaded in another operation.  I can't believe that Ford had more than a couple of stations making them at any one time, and the outside threads, which we probably cut on a lather, are going to be different than the inside threads  because they were cut with different tools.  I don't see the danger in just replacing the damaged spanners.  It would be like replacing a set of drum brake self adjusters.  All the spanners do is move the carrier side to side so you can set backlash without the use of shims. 

I'm not confused about it.  A rebuild book said switching sides on the spanner nuts could possibly cause the nut to push on the bearing seat unevenly, which would cause premature wear.  It basically recommended keeping everything side specific.   That said,  I thought that statement overkill myself, as it seems that would be the job of the bore in the cap itself.  But I did keep mine side specific. 

Mark, are you talking about the big bearing preload nut - the one with all the holes in it?  If so, it is not unheard of for them to look like someone had used a hammer and chisel on them, because someone probably did.  In setting the preload, and the position of the ring gear, if it just needed a "scosh" more adjustment, some people would use a hammer and chisel or big punch to rotate the adjuster nut without loosening the cap.
I really don't think it would damage the usefulness of the nut, it just makes it look ugly, unless it is really severe or there are cracks or stripped/damaged threads on the nut.
Good Luck,
 

The only way the adjuster could put uneven preload on one of the side bearings would be if the threads were not cut square, in which case you'd have a much bigger problem.  I would assume the result would be a noisy gearset and premature bearing failure. 

So long as you can effectively lock the adjusters in place with the locking tabs I wouldn't worry about superficial damage either.  I would clean up any sharp edges but I do that to everything anyway (castings, etc.) to reduce a stress riser related failure.  People don't realize that cracks start as tiny surface imperfections, and if you can eliminate them you can greatly improve the service life of your parts. 

I have had to fix other peoples work several times on the 8 and 9 inch units and yes those backlash/ pre-load adjusting pieces are sometimes really beat up. If the surface that contacts the bearing race and the threads are not boogered up, they should work fine. If you can get the correct backlash and preload with the locking tab securely in a hole, I wouldn't worry about it.

You can replace the caps, but you have to machine a little off the mating surfaces and hone the bearing bore.  Its the same procedure as resizing the big end on a connecting rod.  This is done when swapping to billet caps to improve strength for example.  However, this is a costly procedure, and buying a good used third member is likely a cheaper alternative if you just need a good unit. 

If you need the strength of billet caps this is the only way to do it, and it will also affect the pinion checking distance, adding time to gear set up, though that's simplified if you have a way to measure pinion depth. 

All somewhat academic on an 8" rear, as I've never seen billet caps for them, and when strength is needed the simplest option is going to be to just swap in the stronger 9" rear. 

GP
that's correct i need the spanner nut on the side not the caps
my spanner nuts are damaged beyond using  i know you can't swap caps  but i did'nt think the nut made a difference.

thanks
 

Mark - Now back to your original question.  I searched the interweb and was not able to find a place that sells the carrier adjusters.  I think a local driveline shop may be a source or perhaps an advertised rear-end rebuilder may have some sitting around from a damaged unit.  If they can be had at a reasonable cost, I would probably get 4 to find two that fit reasonably well.  You may find an 8" center section on Craigslist as an option - it may be easier to find an entire unit rather than the parts! Are you just refreshing your unit or making other changes?