My 318 Duster

I dont think 300hp is going to be that easy with the manifolding you now have. But, more importantly, you want as much torque as you can make. I'd run the 318-360 Performer, and add a cam like the XE262 Comp, a more budget choice would be the SUmmit Racing cams. In any case, change the timing CHAIN (new to old cars, eh? ;) ) the fule pump eccentric, the valve springs and seals, and tune it, and it will do just fine. I wouldnt get into it any m,ore than that with this setup.