You will not feel 10 HP at the crank. The wheel HP gain will be 6-7. Is it worth your time?
The reasons that the 340 ran so strong were:
1) 22 more cubes than the 318.
2) Higher compression than the 318.
3) Different heads with larger valves and ports.
4) Better flowing Exhaust manifolds and dual exhaust.
5) 4 barrel intake manifold and carburetor.
6) More aggressive camshaft with stiffer valve springs.
7) Windage tray.
