Putting the reverse cable into the factory choke cable location on the dash could be a possibility that would keep it from being confused with the OD.
My 66 El Camino had the three on the tree with the cable actuated overdrive. I liked that feature. You could even use it in any gear not just third.
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69 C10 shortbed stepside 400 small block - built like what a super sport truck could have been
https://67-72chevytrucks.com/vboard/...d.php?t=484426
69 K20 lwb TBI 350 4L60E NP208 14-bolt Dana-44 w/disc
68 Camaro SS / RS 500hp 439 inch roller cam big block 4L80E