Brake booster and bleeding questions

[msaelens66]

I just converted my 64 c20 to front disc setup with a booster/dual master/ proportioning valve. The rear are drums off a 83 c10. First do I have to have the vacuum port on the booster hooked up or will I just be on manual without vacuum. Stupid cuz why wouldn't you want the assist. Just curious as I have not hooked it up yet and I get a better pedal feel for now. Having said that I can't get Fluid to the rears. Standard bleeding attempted. Bench bled. I have fluid to front and opened line half way to rear and have fluid there. I have had temporary hooked up vacuum by using the line from manifold to pcv but that takes all pedal away while trying to bleed. Any help please?