Would really like the source of the Galen #s, they seem off on several fronts based on personal experience. For example, in 67-68 the 4-speeds were only supposed to go in H & L codes, it just doesn't seem to make any sense that they would appear with standard 350HP 440's.
In the old newsletter "Shifty C-Body Express", there were 2 documented 1967 300 2-door hardtops with L-code & 4-speed in their registry. The 4-speed was reportedly not offered in 1968 Chryslers. One collector supposedly had 2 68 300's but they were never documented; they were likely converted.
See video here of a 67, radio delete & AC no less-
1967 300 4-speed video