A vacuum gauge connected to the engine valley/sump
is an essential item to properly develop a dry sump system to "evacuate" blow-by. Don't be surprised if it takes WAY more pump stages or capacity than you think to create a vacuum. You will need to reverse your crank seals (think about it . . .) OR run seals with a "dual-lip". High levels of vacuum create strange sealing problems within engines. Think carefully about using gaskets Vs. a sealant, ie: RTV.
Serious reduction of the internal "oil mass", MAY create weird wear issues within the engine. Be sure to do a thorough evaluation of components & wear patterns during teardowns. This is VERY important and should not be ignored.
BTW, some engines respond very well to this, others just don't seem to respond with any bhp pickup.
Check out a current WINSTON CUP engine, IF you can get close enough for a picture. Dismiss publicity photos, NOBODY gives away ideas at that level. CUP engines circa 2002 ran 5 stage pumps, 4 scavenge & 1 pressure. And all sorts of oil flow reduction. These engines had 0/1% hot leakdown and pulled at least 5" of crankcase vacuum. Consider for a moment that in 1992 the same engines had 4/7 cfm of dynamic blow-by at WOT on the dyno in the power range . . . . . . .
Think seriously about blow-by reduction in the first place. Blow-by is LOST combustion pressure, ie: horsepower. Do what is necessary to get it sealed up.
Fordboy