Not sure why ya'd go with a rawson drive for a john blue, IMO, ground drive wheel is as good as it gets "k.i.s.s." theory.

Heres what the cost factor vs. more stuff to put in your cab, break, and just plain possibly give ya headaches.  "Hypro pump, shutoffs, etc. with a used monitor for less, and by adding a few more shutoffs turn sections on and off with the planter shutoff system." 

Just giving ya second thought, everything mentioned works, Ive had a hyd pumps before, don't want em back on a planter.  Id take 12 volts pumps before hyd, but like J. blue best for me.   A 60 some foot central fill planter with liquid fert, e-sets, has ALLOT going on.

Best of luck.

Brian