Throughout its service life, the B-52 fleet went through countless updates and mods, and replacement parts had to be matched not just to the model (ala B-52A, B, C, etc.) but the production block # and often the a/c serial #. Even then, techs had to compare parts as record keeping often lagged in those pre-computer days.
My father was a SAC base supply officer for the Wing at Barksdale, and it drove him nuts. He did a good job, and the only way he escaped LeMay's clutches was to get accepted to Command and Staff School.
Shortly after that around '60/61, as a newly minted pilot willing and eager to fly anything that someone would let me and pay for the AvGas, I was on call to fly for Slick Quick Trans out of San Antonio. They contracted to SAC to deliver mission critical parts for their B-52s and KC-135s. We flew fast Aero Commanders, Cessna 310s, P-51s, a P-38, and even two Mosquitos.
The overhaul depot (for J-57s and other B-52 systems) was at Lackland/Kelley maintenance complex, and they'd build components to spec within hours to meet the urgent needs, and we'd deliver. Otherwise, we'd fly to say Dyess, pick up a part, and deliver to Minot in a matter of hours.
A great way to build flight time. Tom Slick was offered some surplus T-33s, but found the WWII recips cheaper to operate, with better range, and overall, faster point to point. (115/145 was $.30/gal)
Alternator/generator/charging systems were especially diverse, far from standardized, and hard to stock at a base level.