Remove Metering Valve from Combo Valve?

[crakarjax]

I want to unscrew the metering valve portion of my combination valve (from a 1972 disc/drum truck, often erroneously called the proportioning or prop valve) but it doesn't look like it's got any hex portion to grab with a wrench. Anyone know the trick to disassemble this?

And on the subject, the same person might know... can I replace the brass flare seats in the valve? It looks like someone jammed a nut down on them at some point, causing a deformation.