If your donor engine (?) was set up with brackets for A/C and the recipient cab (?) already had a/c you could possibly use the donor condensor, compressor and get away with just adding new lines and new dryer. Note: Possibly!
If your cab was not set up with a/c you could just purchase the individual components from Vintage or whoever you choose to use. However, you're adding new stuff to a used system, the inside components aren't cheap individually, and when you get your old/new stuff all plumbed in there's no guarantee it's going to work properly. Conditions in the old system such as "black death" can ruin your new components.
The kits are set up for specific vehicles and my kit from Old Aire came with the proper brackets, compressor, the correct sized condensor, evaporator, controls and a set of installation instructions with a toll-free number if I got into trouble. I've used salvage components before and found that you'd better know what you're doing, and have a friend who is an a/c tech to bail you out when things don't function properly.
I think you would be money ahead and assured of a reliable system, if you planned to go with the package kit. Hope this helps.
Dave
