I disagree with the comments posted.
The size of the master may suit your application......but like u said...there is (may be) a residual
valve in the system. This needs to be removed overwise the brakes will not fully dissengage. I'm pretty sure that these valves exist in all drum brake systems. It is nothing more than a spring and possibly a ball? The best palce to look for this is just under the master cylinder. Where u attach the pipe. IT shoule be somewhere there.