it sounds like you need to sell him on a particular idea and stick to it.. and weather the displaement is 496 or 509 really wont matter, the 496 might be a little more street friendly and will rev slightly less agressively.. and thus be a little less hazardous to drive but thats only marginally.. i think you need to move on to asking hom decitions he can actually make.. does he want the intake polished or satin... and so on... and tell him that you will make the engine fit his needs and ask him to tell you what they are...
i think ka67_72 did a set of equal length BBC turbo headers in stainless.. send him a PM and see if he cant whip you up a set.. looked awesome, the primaries were alittle to large diameter if you asked me.. but it sure looked bling!
http://hotrodders.com/gallery/showph...cat/500/page/1
http://hotrodders.com/gallery/showga...00/ppuser/7803