crap now that I think about it more, the pcv has a check valve. fuel pump wont work right on that one. I dont have a flat head with a fuel pump handy. got a few twins.. they have a port on the crankcase. I have a few OHV's with 2 ports on the pcv plate. might be able to drill a new hole for the pump. Might check with a mower shop, I cant come up with a good model number for a flathead with a fuel pump, should be able to find a factory cover pretty cheap. off the top of my head I cant remember seeing a one holer flatty with an impulse pump. it should work, but I only remember gravity feed set ups.
I have seen guys tap into the dip stick tube for fuel pumps
the Onans were bad about starving for fuel on the old sears. most people put on a cheap adjustable electric.
Why do the relocate? I am not real crazy about having the gas tank too close to the battery, but I have had tractors upsidedown and inside out. never had a fire problem. just keep an eye on the plastic tanks (they crack) and replace the fuel line. its cheap insurance. kink the fuel line, If you see cracks, it needs replaced anyway