And yes the AVS was used on both 383 and 440 in 69 but the 383 used the deeper neck of the two bases. My guess would be because the intake manifold is a bit shorter on the 383 than the 440 or it could be a hood to base seal issue. If you have one of each manifold, perhaps you could check for us Tony.
Terry , the 440 deck height is roughly .750 taller than the 383/400 and that subsequently put the carb about a 1/2" higher on the 440, that's the reason for the different air cleaner base depths .
