I'm looking for the specifications/spring numbers for both the equalizer and bolster springs used on the rebuilt "Boise" Budd cars. If anyone has this information available, it would be greatly appreciated!

Those are the Budd RDCs made into coaches by Morrison-Knudson I believe, I have heard that a few are still in Canada, some were on VRE, etc.. I doubt this would help, but here is a list of original Budd documents, the original springs might be in there. https://www.pullmanlibrary.org/2022-4-15BUDD.pdf You might try Wabtec, which bought MK/ later Motive Power Inc..

Don't forget the fleet on the Grand Canyon Railway--i half expect Brother Hadder to chime in when he has time.