The mechanical pump has a breather hole on the body, and part of the function besides venting is that mechanical fuel pressure is regulated according to atmospheric pressure (as if carbureted cars aren't rich enough at high altitude, who wants the pump over-pumping?).
Drill and tap carefully for a pipe-thread hose nipple and connect to boost above the carb. At lower boost pressure it can't overload the pump. At higher pressure (at 8+ I'd watch it carefully for awhile) it may rupture the diaphragm.
Attached is the instructions from Paxton for Rustangs, but I found similar instructions at one time for the Mr. Norm's kit, and they were similar. Page 19.
