I have a 69 as well. I have an Isky 280 mega onboard. Prior to this I rebuilt the stock brake system. This included a replacement booster and master cylinder from SSBC, all stainless lines from Mustangs Unlimited, stainless steel braided front hoses from Russell Performance, new drum/pads/hardware/cylinders in the rear, and so far it breaks better than I thought it would. I have been thinking of rear disc as well, but so far have no need. I have low vacum as well between 9 and 11. There have been times I have had to brake in front of some stop lights, the car stopped well for what it's worth. I would think if more vacum is what you really want, go with a pump. I am not sure what it is that makes my set up work, I just think it's the combination of newer parts and all. Hope this helps, best of luck. but that's my .02 worth.
