No worries, installing an original factory airconditioner in an old car would be one of the most difficult jobs possible .
The early Commodores had no cabin air filter and a horizontal evaporator- this forms a natural litter trap which turns into a compost heap when wetted by the airconditioner operating- which rots out the evaporator coil. A picture of mine when I removed it is attached.
If your evaporator needs replacing you can double the cost of the job.
I'd try and use as many VK AC components as I could find. I doubt that you will find a VK evaporator but you might be able to buy and modify a VS/VR one for under $500. I used a Sanden compressor for my A/C rebuild- it fits on that bracket. And you will be stuck with using R134A gas or its later replacements.
You need to work out what you need before you start.
Kudos for your rebuild.
Thinking with the popularity of our cars it won't be long before someone fabricates an evaporator.
The heavy AC pipes can be rebuilt. They rebuild the metal fitting on new hose......had mine replaced along with condenser and compressor.
Weakness with our cars is they ran colder with R12. Using VP condenser and newer R123A isn't as cold but ok. People often overlook the belt which dries out because of power steering seeps from pump front seal. Any slipping is hard to notice but but can be picked up with strobe torch under reving torque load......makes a big difference.
How did you deal with inevitable plastic tab cracks and breaks?
Mine is 08/ 91. Would Mine have a filter I can access and replace? Where?
Remember a couple of years ago replacing fan resistor looking down into evaporator with a a torch and only seeing 3 or 4 eucalyptus leaves. Never see any leaves under plenum cover. Do you think they get in from elsewhere?
Unbelievable that photo really the amount of crap.