for reasons UNKNOWN the "US shipped 1968 Charger OPTION & ACCESSORY Report" is in ERROR - it shows 0 "zero" 3-speed manual transmission installed ***** the 4-speed numbers are in ERROR also
the 3-speed manual (column shift) transmission was the STANDARD transmission behind the 318 V8 & the mid-year introduced 225 /6 (an automatic transmission was a ~$200 OPTION)

from WARD's AUTOMOTIVE YEARBOOK (1968 model year):

96,108 = total 1968 Dodge Chargers

90.4% = 86,881 = total 1968 Dodge Chargers with automatic transmission
7.2% = 6,920 = total 1968 Dodge Chargers with 4-speed manual transmission (all floor shift & 383, 440, HEMI)
2.4% = 2,307 = total 1968 Dodge Chargers with 3-speed manual transmission (all column shift & 225, 318)

99.0% = 195,147 = total 1968 Dodge Chargers with V-8
1.0% = 961 = total 1968 Dodge Chargers with /6

the manner in which these numbers are calculated results in a number that is accurate to +/- 48 cars (0.05%)
"IF" the installation rate for the 3-speed manual transmission was the same for 225 & 318 powered Chargers, ~60 /6 Chargers would have been built with the 3-speed manual transmission for the 1968 model year