Rarity (and desirability) of a slant six/ factory 4 speed?

The 274-4 4 speeds and automatics in 65 Barracudas are almost 50/50. I don't have numbers for the slants. It is what it is. More desirable as a 4 speed. May be the cr is worth $500 or more with a 4 gear vs a 3 speed or automatic. Not enough to make a big difference.