Modifying a dual plane??

I have a buddy that races v mods and they build their own engines. He says just adding a one inch spacer nearly always added 15 hp on the dyno. I am building my 440 for my Ramcharger that will be street driven. He told me to make sure the cam and intake matched power ranges and to make sure I went dual plane so I would have good streetable power. I had my eye on a single plane and he said if I was racing it would be okay, but I would lose some torque but gain top end speed. Keep the divider in place.