If you want more piston options, pick up a set of L99 (4.3L baby LT1) rods. They are 5.94" long powdered metal. With these you can use pistons from a 350. I'm using these in my 302 although mine will be built for high RPM's.

If you want decent mileage I would use 1.94/1.5 heads and for the most bang for the buck I would also use Vortec heads. The 2.02 heads are really too big for a mileage engine. They will hurt the low end torque---less MPG.