Whats wrong with my Dusters front end?

In my experience, the issue of a car not returning to straight when turned is a lack of toe in. 0º toe in will reduce tire wear and initial steering effort to turn. It's a question of what you're willing to trade off.

Factory settings for the 71 Duster are:
Toe in 3/32 - 5/32 inch
Camber LH 0º 15' - 0º 45' positive
RH 0º 0' - 0º 30' positive
Caster 0º 15' to 1º 15" positive

Bear in mind these cars were originally built with bias ply tires. Radial tires respond a bit differently. Here are the settings I use on the Darts.

Toe in 1/16"
Camber 1º 30' both sides
Caster 2.5º positive (all that either chassis would allow)

Both cars have 60 series radial tires on 7" rims and power steering. Steering effort is slightly higher, turn-in much sharper than the older settings. Recommend setting ride height before adjusting suspension.