Nice truck here are a couple of suggestions. Do not know if GMC and Chevy big truck brakes are the same but here are the spec pages for 46 and 48, 47 is missing. I would assume chevy 4000 series is same as GMC 450?? Quick measurement should get you to the right series.
http://chevy.oldcarmanualproject.com...resto/4885.htm
http://chevy.oldcarmanualproject.com...resto/4676.htm
The TF factory assembly manual has very detailed information on how the components go together, I assume the AD will have the same, but again do not know if GMC FAM is available or Chevy is the same. I will dig thru my Dads old manuals, looked quickly and only one I could find was 60-69, but I know he had them for the AD trucks because we used them when I was a kid.
Also see if there is a big truck jobber near you. Those same trucks were used by farmers for hauling grain etc. so there would have been lots of sources for parts. Here in Boise we still have one old time shop that is pretty good at working on old chassis, etc, that "modern" guys and equipment cannot fix. An older over the road repair place that services big trucks might be able to help too.
edit here is a link to an original factory shop manual for 47 450 for sale:
http://www.faxonautoliterature.com/1...l--P15783.aspx
Here is a link to a 47 master parts manual:
http://www.faxonautoliterature.com/1...et-P26067.aspx
I found those with a quick google search. The parts manual should give you numbers to start with.