What is the best black original looking front shock for a 74 Duster?

Yikes! That's scary looking with those cinder blocks under there! I wouldn't use those air shocks either. Beside the poor ride quality, if you have one blow out for some reason, under certain circumstances, you might lose control of the car. I saw two different accidents due to sudden air shock failure. Both had oversize tires that the quarter panel would hit if not for the air shocks. One had individual air lines, the other had one line that ganged both sides. The first one, when the line blew due to getting melted on the exhaust pipe, dropped one side down to where the body locked onto that one tire. Car took an immediate turn, ran off the road and into a tree. Second car had both wheels suddenly lock up due to the quarters clamping down on them, and slid to a stop so suddenly (and without brake lights) that the car behind it ran into the back totalling both cars. They figured afterward that the lines didn't have enough slack in them and pulled out of their fittings after hitting a large bump in the road.