supercharger would be the way to go ... but perhaps it's me, however I cringe at the thought of spending money on a 6 when it will always be slower than an 8 ... particularly if you do a cam or forced induction on that!
Each to their own though.
Actually it just reminded me of a 67 or 68 camaro I saw on ebay in the states ... it looked wild ... full custom exterior, interior ... with a twin turbo 1000+HP engine ... BUT IT WAS A FOUR OR SIX CYLINDER nissan or equivalent. I just couldn't do it ... made me cry. Camaros deserve a 502, or 572 ... not a little buzz box engine.