Hydro-boost conversion (there is a string on this w/part numbers in this forum) if you don't already have hydro-boost is biggest bang for buck as the clamping force increase is the desired result. Understand that you would need high pressure p/s pump and cooler in most hydro boost brake up-fitting projects. Vacuum, hydro-boost or hydro-electric all have their place when up-fitting brake system, however, there are many specialized brake up-fitters who more likely than not sell complete kits for your desired results and application.
1999 GMC K2500 BURBAN, NAVISTAR enhanced 6.5 td aftercooled, dual alt's, PSC p/s pump w/HD cooler, redundant FSD's, HEATH program, turbine/downpipe wrapped, 4" SS exhaust, real time OBD2 data logging w/device controller, EVANS waterless coolant @ zero (0) psi & 135 gpm pump, 4L80e w/kevlar and premium steel w/cryo treated input/output shafts running @ 100 deg. F & 140 deg F towing, all synthetic fluids, AMSOIL bypass system, MileMarker hydro, dual fuel tanks, and on and on, questions PM me.