i went with the vacuum setup, this was when Greg used to work at Schuman Carriage (the olden days), he had the whole parts list for converting GN's to vac brakes, and got the GM parts to "enthusiasts" at a VERY steep discount, closest thing to a "kit". i guess this was before hydroboost was invented... if you're ordering parts, you should consider RockAuto also, they're pretty quick, even for Hawaii.
yup, this doesn't help much...