Sure it can still be a GO.
Forged pistons, good heads, 4 bolt main,forged steel crank, ballanced lightened reciprocating assembly and valve train (girdled) 5000 stall. 4.88-5.13 axle ratio. 12/1 13/1 compression Tunnel Ram Intake with 2 850s. RPM-Range (4500-8500) roller cam Valve Lift (.727 .727) Valve Lash hot (.030 .030) ADV Duration (330 330) .050 Duration (288 288) LC 108. that's one
BIG MONEY!!!!!!! LOL WE could suggest anything !!!!
Or a stock 396 2 bolt main 325 HP, forged stock pistons & rods, the heads you have and supercharge it at about 7 to 10 pounds boost with a mild force induction cam 500 hp is easy and street able max RPM around 5500 a lot cheaper!! Or spray it that's even cheaper.
500 HP out of a normally aspirated single carb 396 325 HP engine with stock bore calls for very high compression and big money! The 65 396 was called the fat block because of the cylinder wall thickness and could be bored to extremes so if that's the block you have you have a lot to work with, 4 bolt mains your best choice , the 2 bolt mains limit your build depends where your money runs out " MONEY = HP, TORQUE, and SPEED"
Cylinder-Head Flow-Bench Database
GM 702 Iron Oval Port an early 396ci and 427ci closed-chamber head used only in ’65 and ’66. This head virtually clones the GM 290’s flow numbers. While the 049 head flows much better the 049s would drop compression two full points. The best set up here is to either give up some power and use the GM 702 head you don't lose much or go with the better GM 049 head and Open chamber pistons to match.
GM 049 Iron Oval Port This Open chamber oval-port head saw use in a number of 402ci to 454ci big blocks from ’73-’84. Of the three stock iron oval-port this one was the strongest. Again, like other production heads, if horsepower is your goal, larger valves are the way with these heads