what did the car originally have in it motor wise? was it a slant six or a 318? either way you should probably go with a larger torsion bar.
you have a 73-up style disc brake system on the car.
what numbers are different for a 73 that you are talking about??
what year car are you working on? the pitman arm and idler arms i posted were for a 70. 73-up will be a different number...
refer to this list for the part numbers.. http://www.bigblockdart.com/techpages/moognumbers.shtml
73-up pitman arm is powersteering K7076.... manual steering K7075
73-up idler arm is K7086