Looking for a little more power out of a 318

If you're planning a 360 for later, I'd run the 318 until you can put it in. To get the kind of power you're looking for from the 318, you're looking at laying out quite a few dollars. IMO the outlay doesn't make sense if you're going to swap engines ASAP.

I'm going to agree with Rumblefish that according to the formula, a 318 @ 85% volumetric efficiency can get by with a 500 cfm carb. Personally, I went with a bigger carb because that's what Mopar stuck on the HP 273 running less cam than I am.

You'll need a different driver's side engine mount for the 360. Also, if you use an aluminum intake, you'll need a fiber intake gasket set.

My Demon engine is a 318 with 302 heads. I'm very pleased with it as a "driver". Pistons are made to the specs of the early LA 318 when it had a 9.2:1 compression ratio. With the 302 heads, I believe it bumps it up a little more. I have a .441 lift cam 218/228 @ .050 lift. The intake is an Eddy Performer (small ports to match head) topped off by a 625 cfm AFB. It also has a double roller timing chain. I'm using a 360 A-body exhaust manifold on the driver's side and a Magnum V-8 one on the passenger side. Other than that, the motor is pure stock with no machining. The combination runs well on mid-grade gas and throttle response is quite good with 3.23 gears. I'm going to estimate around 275 hp.