318 buid up.

I'd suggest looking at any 318 from around 85 to about 91 from a truck van or dippy, this should get you what you are after. Someone told me recently that the stock cr on these motors is in the high 8's. So theoretically if you shave the heads a little and use thin gaskets you can get a solid 9 to 1 motor out of using more or less stock parts. If you replace the pistons Ive heard that the 318 magnum pistons give a little more CR in the older motors, and are a direct replacement. If you intend to use the #302 closed chamber heads - plan on porting and increasing the valve size, for a mild 318 use the stock 340 cam. You could also use the magnum heads more or less as is and be good to go and save money and time over the #302 casting head. The magnum heads require a conversion that is all do-able using stock parts.