[Eyegore]

Welcome fellow zonie, be patient they all come together. I suggest you watch craiglist and check the local wrecking yards - look for the pull a parts, their the better ones allowing you to go inside and pull the partrs off yourself. I believe the parts that work for your truck are 73-79, perhaps 80 also. The 86 doors should work, but the earlier door panels will not. I suggest you check the LMC online catalog to help you out to see which ones match.
Also this group on here is a great resource and are full of suggestions to help you with your project.
Hang in there and have fun.