318 Mopar vs. 340 Mopar

318`s were really not built around performance, most are lo-po 2 barrel engines while 340`s (68-71) came with 10.5 to 1 compression, windage trays, forged steel cranks, double roller timing chains, 2.02 intake valves, 3/4 cams, HD valve springs, and dual plane intakes. I`m sure I`ve overlooked things too, but you get the idea. No matter which engine you choose to replace your slant 6 with ,whether it`s a 318, 340, or 360 you will need to build the rest of the car to match. The car will get heavier, go faster, and handle less nimbly so an upgrade to brakes, cooling, suspension, and other drivetrain parts will/may be necessary. My vote would be to find a 360 as a building block. They`re still easy to find and have a lot of potential. Figure in some extra bucks though for upgrades to the rest of the car.