Like rb446 said.. a rebuilt double pumper will do more for the "seat of the pants" dyno than almost anything. Trust me I dumped a bunch of money into my old 3310 before stepping up to my 850 double pumper.. bolted on the 850.. felt like I picked up 30hp right off the bat. Truly awesome ! .. those heads are capable of handling much more cam without porting. That cam will hold back your porting gains. More cam and carb will do more for that good intake and exhaust without grinding away on a chunk of cast iron for 40 hrs !! I understand the time vs. money arguement.. but beg ,borrow or steal a double pumper !! You won't regret it. Lol.