it is up to you but if you just shiny up the surface of the lower bypass cover for ex.: on 100 grit paper and make a patterned cover plate of 1/16 aluminum you could mount the pump on the cover plate and drill a 1/4 inch hole in the best quadrant aligned to the pump’s rear center pulse port
Me I would try to use a lower quadrant corner edge allowing any accumulated fuel/oil pushed in the void behind the pump to simply drain back into the crankcase . This will prevent any puddle of fuel staying in the bypass cover. pick a quadrant and drill at a slight down angle. remove the bypass to drill it !!!
other quadrants can be filled with JB to eliminate any chance of the “extra” volume affecting the pump operation or crankcase pressure specs
seal the aluminum plate /pump assembly over the drilled bypass cover with either a paper gasket cut to shape or gasket sealant
the crankcase does not generate high piston like PSI’s since on the downstroke it pushes new fuel in the cyl and expels burnt fuel at the same time. On the upstroke it sucks fuel from the carb.
both these actions will pulse your new pump directly or via a brass nipple tapped in..
OK I have never done a big twin so it is all up to you Option#1….you drill, plate and mount a 2 nipple pump or Option #2 you mount a 3 nipple B&S pump anywhere you can and hook up your pulse line to a brass nipple tapped into a bypass port as per the pictures above..
this latter option may be your best if you are worried with option 1 (drilled and plated bypass cover ).
up to you now.
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