Looking to get a set of custom headers built for my 71 Plymouth duster. Would like to know some recommendations on header tube size and length. The car as tube k-member with rack and pinion so i have plenty of room.

Some of the engine specs.(Small block)
360-1 Indy heads CNC
3.79 stroke, 4.060 bore 394 ci
14:1 comp
1050 domnator carb
roller cam ??????
weight just guessing 3000-3100lbs.

Should I builg 1 7/8-2 inch steps.
2-2 1/8 steps
or straight 2 inch.

Any suggestions or advice would be appreicited. thanks.