Thanks for the info guys. It looks like I'm going to need get get fittings no matter how I do this.
The Proportioning Valve has 5/16" thread (3/16" line) on the IN and OUT side of the valve.
The metering block has a 7/16" (1/4" line) coming out of the back and going to the rear.
The 1/4" line I got from the part store has 3/8 fittings on the ends.
Looks like I'm just going to take the stuff to NAPA and ask them how to do this.