17x8 fit on stock 73 Duster?

with 17x9 you need about 5.62 or 5.5 backspacing.

Here's a Valiant with the same 17x8 and 5.62 backspacing as pictured above. Some rims come closer to the outer tie rod than others. You need the flat upper ball joints though.

http://www.moparfins.com/CLAIRDAVIS/1969_front_end.htm
http://www.moparfins.com/CLAIRDAVIS/Cobra_Wheel.htm