You don't need a check valve on any motor for it to be an ideal setup. My 'Ova da hump' valve concept is for high Hg" vacs to be used in conjunction with high CFM/Low Hg" to get over the hump & start building negative pressure with the little pump. It is mostly for guys with pucks, vacuum bagging or vacuum forming.
You should most definitely run filtration on those motors. An automotive air filter or cylindrical shopvac filter (Rigid brand ones work well) to keep anything the bleeder misses or chunks/debris when you first fire up your system. Also, put a little filter/breather on your bleeder holes for the vac cooling holes so that junk doesn't get into the pump that way. Cheap insurance...Few even think about the little PVC chips that are stuck to the inside of pipes when you cut them while plumbing the system the first time...
-B