They should be using a quality double roller chain and include a feature in the vacuum pump such as a pin that can break if the unit locks up... or run the vacuum pump off of the undriven end of a camshaft...or both..
Simple is MUCH better ,, these cars are very crowded underhood and there is quite a bit of heat to get rid of... personally I’d go without brake boost it’s not needed on this car.
Vacuum in and of itself is created by lifting the gas pedal as the engine starts to suck.
It was originally used as free energy to assist in shifting an automatic transmission.
Why a “vacuum pump” is needed for braking is beyond me. Power brakes as well as power steering came from “positive” energy.
As I consider this, it seems that any device that is driven directly from the drive train is not a true vacuum device.
It may be that it is labeled as such, but it seems to be more complexity than needed.