250 HP will produce lots of tire smoke and you don't need expensive porting to get there. You can get 300-325 HP with a non ported head on a 318 with good parts choices.
Here's what I did to mine. Comp HE268H cam, 1 5/8" headers, Weiand 8007 intake, opened up the port entrance on the heads to match the intake (gasket match) and a Summit 600cfm carb. I also run a 3.55 suregrip 8 3/4 rear.
It runs well for what it is and will get me by until I get my new engine built.
