225 performance upgrades without pulling engine

Gday guys, Im from Australia and own a 66 VC Valiant Regal with a completely stock 225 aside from the addition of electronic ignition. Im wanting to know if putting an Aussiespeed Longrunner 2 bbl manifold and perhaps 400cfm 2bbl carb with extractors is overkill? Or would I be better off just using a 2 bbl short runner manifold and smaller carb? Im not wanting to pull the engine out at this stage by the way, Im just after the right advice for a few extra horses with bolt on gear for now, thanks guys