not a Dart but same shifter,I had the same thoughts about where a stock 4-speed location would be

I went with what felt good

one suggestion...cut the hole for the cable first,put it thru the rubber groumet installed in the floor,then mark holes for shifter and mount it to foor,then bolt cable to shifter

I was a ruff 1/4" off had to it just a tad for the cable and groumet to fit and bolt to shifter

i like the shifter,it will work good with the CRT-FMVB I have