Remember for a TKO -600 it will require major modifications to the floor tunnel to fit in the car - from the firewall to the just under the front seat edge (for 61 to 64 Chevy's for sure)
You have to cut out the entire tunnel and make a new taller tunnel cover. If you have carpet in the car I bet it will not fit the higher tunnel (my point is the carpet has to be taller and wider (You might have to start with new carpet )-I think this comment is correct
Modifying the tunnel is a major reason is why I went with a Richmond 5 Speed or now a Richmond 6 speed ( zero tunnel modifications needed)
plus I wanted a transmission that shifts like a Muncie. 4 speed and has overdrive. I drove a friends 61 Chevy with a Richmond 5 speed to check out how it shifted.
Finally I wanted my factory 1962 SS shift plate to fit on the existing tunnel and fit around the Hurst 5 speed shifter on the Richmond 5 speed.
I have one 62 Chevy 327/300 HP convertible with a 700R4. I prefer 4 speeds or the 5 speeds by far way --to much fun to drive....
I bought the 62 with the 700R4. All my other cars were restored with 4 speeds or the most recent 5 speed in my 62 SS 409 Convertible
Paul