Tim,
Steering stuff can get pretty arcane at times. The KEY here is MOST '63 - '87 pieces will interchange as long as you stay in the same series; C-10, C-20, C-30. Somewhere around 1970, the A arm bushings changed from bronze to nylon/plastic. Some time around 1980, GM switched from SAE to metric/o-ring fittings on pumps and steering boxes. Power steering MUST have the matching pitman arm, and manual steering MUST have it's specific pitman arm. No exceptions. Idler arms SEEM to all be the same, but there are several part numbers. I personally like to get everything I can from a doner truck and rebuild what needs it in order to keep all the pieces the same year model, but that is just me. I have been told that there are different tie rod end sizes within the C-10 series, but I have NOT run into this.
I'm sorry this is late and I hope it is a help. Use this info any way you want, but NEVER take it as a bottom line!
Best wishes,
Les