Hey RAII4_speed, The 1970 Duster 340 came standard with the 4 piston caliper Kelsey Hayes disc brakes as standard equipment.The power assist was an option. 71 and 72 drum brakes were standard and power assist was again an option as well as disc brakes were now an option. the 1973 Duster 340 came standard with disc brakes.This year (1973) it also became the 4.5 inch bolt pattern wheel instead of the 4.00 inch bolt pattern wheel like the 70,71 and 72 used.Hope this helps you out.