I'm no expert but I don't see any 360 getting better than 8mpg unless you do some deck shaving. It lacks the efficientcy of quench. And thats only if you really wanted to stick w/ the 360 for whatever reason. At that point, I'd just get the 390 crank/rods to complete a great setup for 30+ cubes more. Also, when bumping up the compression on a 360, you're still running weaker rods than that of the sister 390. So it's almost a no brainer. Build a 390, pass rice burners/chiivy lovers grinning.