The 1970 "Slap Stik" shifter is indeed a one year only piece because of the round handle. The black slider piece has a round hole instead of the oval hole used on 1971-1973 shifters which had the black plastic "T" handle shifter.
Now in 1974 they went back to the round wood grain ball but the clear plastic lens no longer said "Slap Stik", and I don't believe the 74 shifters had that ability.
$300 is a tad high in my opinion, but they are getting harder to find