From my younger days and my experience of running a 396 BB in a 4x4 (6500 lbs) making 14.88 at 95 and getting almost 18 mpg when babied back in the "stayin' alive at 55" days here's my suggestions.
Look at a cam hydraulic cam of about 230 at .050 with .500 lift, ad a set of Rohdes lifters. Put in lots of cold air. They now make dual snorkle air filters. Do a little head clean up and a good exhaust system, 2.5" mandrel bent. Use a 2500 stall converter. You'll also want a good ingnition system that is well set up.
The reference I used to build the motor was primarily a bunch of tips picked up from a book called "Performance with Economy". The title was enough to turn off any performance guy, but to this day I believe it is the best book I have for building any engine.