And now for an answer about the 1990 318, not the "MAG" motor. CompCams offers a bolt-in replacement roller cam that has .450" lift, but is a stock-replacement, meaning, and I asked them, it's a bolt-in as far as the electronics are concerned -under $300. You will need to replace the valvesprings because of the very nice increase in lift. The stock 318 cam is a joke (.385"/.400" intake/exhaust). The stock valvetrain is easily able to handle these upgrades. By all means, do it. If you're using the TBI, open up the exhaust with a good cat-back system. If you wanna go carb, that's another matter....more options. A fresh 318 will respond very well to just a cam change, easily more than a stock '90 360. Naturally, an equally modded 360 will always be more since, especially where torque is concerned, it is swinging 42 more cubes. Your other memories about the two engines are correct. The pre-Magnum 318's have smaller ports which are great for maintaining high flow velocities which really fills the cylinders. The stock '90 318 has a torque peak at something like 2,000 rpm, so you can imagine just how even a modest cam will help.