Paul, as far as internal mechanical differences, besides the camshaft, wouldn't the 67 versions have the
small chamber cylinder heads as opposed to the 68's & 69's?
The 1967 383/325 HP had;
> #2406516 Cylinder Heads
> Restrictive {Driver-Side} Exhaust Manifold
> Low-Rise Intake Manifold
> Carter AFB {575 CFM rated}
> 4-Blade Fan {Direct mount to Water Pump}
The 1967 383/325 HP and 1968 383/330 HP had the same;
> Compression Ratio {10.0-1}
> Camshaft {.425"/.437" Lift ~ 256*/260* Duration ~ 32* Overlap}
> Valve Springs {#134 lbs. Valve-Closed ~ #208 lbs. Valve Open}
The 1968 383/330 HP {non Road Runner and Super Bee 383/335 HP} sure had a
few more ingredients over the 1967 383/325 HP
