replacing the brake block

[AmadeusCharger500]

I have installed all new brake lines, mast cylinder, Calipers, basically everthing new front to rear except the brake block. I can't get the fluid to pump through the brake block (proportioning valve?) Can I take this apart and clean it or do I just have to replace it.
If replacing it, Will I need to redo all my brake fittings for a newer style block?

[Chryco Psycho]

it can be disassembled , afterall it was assembled at some point !!
if you replace it you may have to modify & reflare a lot of brake lines