Rear brakes locking

Im having problem with my brakes. The rear brakes (drums) locks before the front (disk).

My setup is very simple with old Volvo stuff and i have seen many cars with the same parts. In the rear i have a 9" from a -58 Ford Thunderbird.

I have two adjustable reducers (Wilwood and Volvo original) but the problem is pretty much the same. I have also changed the rear cylinders to 19 mm wich i belive is the smallest available for the 9" Ford.

I have also tested to switch the brake lines on the main cylinder and still no result.

Can someone give me som pointers what to look for? I would be really greatful.

Is the master cylinder for drum rear and disk front or is it a disk front and disk back master cylinder.....????