would you prefer this:
get a set of domed pistons say 5cc (forged), forged rods, forged crank.
buy a set of 180cc aluminum heads with 64cc chambers, make sure they have a very thick hard deck (cause they cost less to machine) with 1.94 intake valves, send them to a very reputable head shop and have them put 2.00 int valves (larger valves would be a big help but they wont fit in the 3.766 .030 over bore with enough clearance) in and have them mill them down about .090" to get you to about 50-52cc chambers (
) you will need to send them your single plane intake as well so that they mill it down to match the heads, also have them go in and CNC the heads to about 205-210cc and able to flow around 300cfm @ .600". buy a solid roller cam with around 250° @ .050 and around .600" lift. blueprint the bottom end to reduce everybit of friction you can (= free hp) and also have the bottom end balanced to very tight tolerances, use a good ATI damper (i would call them) have a Holley 750cfm DP carb worked with dual 50cc pumps, butterflies shaved...i would go with a thicker quench say .050" and do some serious mock up to make sure that the valves have plenty of clearnance at TDC. after all this i would take the motor to a reputable dyno shop and have them completely test and tune it. $$$$ you will likely have everybit of 8000-9000 into all this
with all this you should have a motor that will turn a 305 up to around 7800-8200 and if i had to guess it would be the low 500hp range.