From what I gathered when mine died,I was told all the "pods" will fit the original cam drive,whether they came off cam drive or belt driven pumps..and I swapped just the pod off a donor ,onto mine without removing the unit from the engine,it is just two bolts..
I read online that the pods off earlier Fords also fit and work,and seem to last longer than the GM ones,the only difference is the hose nipple might end up in a different spot..
Prices are insane for new GM ones too--100-200 bucks,when they used to sell for 25-35 bucks back in the day when the trucks were not that old!..pretty steep for something that basically is an oversized fuel pump diaphram..(or EGR valve "guts!")..
(I wouldn't doubt that a fuel pump or EGR would work with a little modification ,if it would bolt up!)...
Some later diesels have electric vacuum pumps (Fords),but they claim they wont last long if used "constantly" to supply vacuum for the transmission modulator or power brakes with a vacuum booster...
I thought about trying a salvage yard used one,but a member here was kind enough to send me a pump he had leftover,so I used that..
I did an autopsy on my original one by grinding away the folded over edges of the "can"--there is a slotted disc washer inside,like a EGR valve has,a large coil spring,and a breather flapper dewhickey made into one half of the "can"...and the diaphram,which was only torn about 1" long,right near the outer edge where its pinched by the two halves of the can...