You would need the vacuum pump to run the brake booster cannister, power brakes being almost a requirement. Granted, you could convert to a hydraboost setup...but...the most common donor source for 6BT's over here is from Dodge pickups, and all those 6BT's are equipped with a multisection ancillary pump asssembly which consists of a vacuum pump section and a power steering pump section. In other words, the vacuum source is possibly already there for your use if you're using a Dodge donor.why would i need a vacume pump? if its for brakes? i would simply use a common alternator with pump built in theyre very common here.