Brake fluid being rejected from master cylinder?

[jbassC10]

I'm thinking the master cylinder I was given to buy was the wrong one for the wrong year and I didn't know that yet installed it and it's cause the back pressure or there's something I'm missing?

I've bought a new one which you can see in the photos that looks different where this one is for the correct year 69.

I've bled and bled and BLED the brake lines, checked for air leaks in the line yet I haven't solved the problem?

I've asked a few auto placees (auto zone, auto parts..) and they've all given me different anwsers.
So here I am my Chevy family, lol I'm here to ask what's up?

I was told by one guy I need a "brake valve" or "balancer/valve" to level out the correct brake presure... soooo ??? What's up guys....? What am I missing?