Re-build one of your late '60s engines. Steel crank, flat top pistons stock,resize the rods c/w ARP bolts, windage tray, file fit moly rings. Generally a lower duration cam with yield more power at lower rpm, like the Lunati 60302. Cast heads with larger valves, port the heads in 'line of site'. The more valve you can see from outside the port, the faster the airflow; along with the traditional bowl enlargement because of the bigger valves. Remove material from the area just inside the intake port where it curves in to allow for the head bolt. Little things like back cutting all the valves to the seating line can yeild up to 13% more flow. Aim for a 9:1 compression, good intake, good exhaust, and rework the distributor a bit.
I always try to remember that the bottom end has to stay together, and the top end is all about air in and air out.
