brake problems on conversion!!!

Again, converting my drum drum 62 impala to power brakes and a dual MC from a single bowl non power setup.

Everything is installed and I have absolutely no pedal. This is the 3rd kit I've put on thinking the MC's were bad on the others, but no change.
MC is properly bench bled and there are no leaks in the lines.
I moved to the lower hole on the brake pedal and it changed nothing.
When bleeding the brakes, barely any fluid comes out in the rears.
I've tried bleeding them with two people method and with a hand held manual pump, same results.
Am I missing something? Is there a check valve I'm missing maybe?
Brakes worked fine before the upgrade, just wanted a safer setup.
Please Help!

When you bench bled the MC, did you make sure to depress the piston until it got stiff (harder to push in)? I forgot this step when I did a front disk conversion on my 70 C10 and had no pedal nor fluid coming out when trying to bleed the brakes.

We did bleed the MC till it was incredibly hard to push in.
We tested it again by taking it off and caping the front bowl and leaving the rear off. Fluid seemed to barely spit out the back, but if you put your finger over it, after about 3 pumps it would push your finger off and spray a little bit more fluid.
We added about 6 feet of line and I'm wondering if there is just so much empty line that no pressure can build up?

Any time you go to bleed the rear brakes and you get at little fluid, generally means you have a lot
of air in the system. You have to keep bleeding until you starting building up pressure. If you cannot get a build up of pressure means there is a opening so where in the system. You need to check all connection, wheel cylinders that a seals have not pop out and brakes adjusted properly. If you decided to use synthetic brake fluid that can created leaks. I would no recommend using synthetic brake fluid.\