Did they ever produce a slant 6 4 speed with a console in 1966?

Yes, you could get a 4-speed with console in your new 225-powered '66 Dart…

…if you were in Spain, buying one of the Darts built there by Barreiros. If you were in the U.S., however, you were outta luck; your choices were a 4-speed (with a 273 engine) or a Slant-6 (with 3-speed automatic or manual). In the U.S., the 4-speed was offered with the Slant-6 only in '64 and '65, and then not again until '75 when the 833OD was offered.

(In Canada, however, you could buy your new '66 Dart-shaped Valiant with a 225 and 4-speed.)