Adding Power Brakes to 66 can't get bleed or any pedal

[buildinga55]

I bought a kit that included the booster, master cylinder, brackets etc. for a 66 chevy pickup. I split the brake line at the T on the passenger side and ran a new one to the new MC, I have done this a few times worked well. I cannot seem to get the brakes bleed. I even went and bought another master cylinder thinking the one in the kit was bad. I have bench bled it 3 times, checked all fittings, fluid will gravity flow out of the bleeders, but pedal goes to the floor and will barely even stop the truck at 5 miles an hour. I am at the point I dont know what to do. I have never had this issue bleeding brakes, I have probably bled brakes on 50 cars in my life and never had this trouble. I bought a booster for Drum Drum brakes since that is what I have on the truck. Any ideas?