I may have had the good fortune to stumble on enough parts to build a factory A/C system for my brother's 83 Dodge van with a slant six. The parts will be coming from numerous sources, all of which are members here. Thanks guys!

The system is from an 83-90 (various donor vans) Dodge van. The compressor sat outside for an unknown (but short) amount of time with no hoses attached to the top. The guts of the compressor were open to the air, but only through the small holes on the top of the compressor where the vacuum and pressure lines attach. With a little Knock 'Er Loose sprayed down the holes and a little persuasion, the compressor turns freely and make no grinding or scraping noise. It does make a pleasant sucking noise though, kind of like a small whoosh.

Anyway, I would like to piece the system back together and install it on my brother's van. Since the system is already discharged, I would also like to convert it to R-134A. I know this entails completely draining the old oil out of the compressor (mostly done anyway) and replacing all the o-rings and other seals in the system.

Here is/are the question(s):

(1) Should I worry about rebuilding/replacing the compressor I have? Any way to test it? I don;t want to put the whole system back together just to have the compressor fail due to corrosion or bad seals due to suitting outside.

(2) What else in involved in correctly retrofitting an A/C system to R-134A? I have a can of refrigerant/sealant from Autozone as well as a set of A/C manifold guages. Autozone also sells the o-rings and lubricating oil. Do I need more?

Thanks!

Yes, it's junk after sitting exposed to the elements like that for so long, regardless of your having freed it up with penetrating oil. You will also be smart to install a new "H-valve" (expansion valve).
Yes. Start by safely getting rid of that goo from Autozone. You neither want nor need "sealant" clogging up your system, and the $20 "R134a retrofit kits" from Harry Homeowner types of outlets like Autozone are well known for causing expensive and extensive system damage.

Doing a 134a retrofit correctly so that the system works well and lasts long enough to make the effort worthwhile means:

Very carefully inspecting all hoses and very likely having some or all of them re-hosed with barrier hose material so that the R134a doesn't seep right through them

Installing all new R134a-compatible O-rings (green HNBR or blue Neoprene)

Installing a parallel-flow condenser (see Here or Here or Here)

Thoroughly flushing the system and adding the correct amount of the correct oil

Installing a new R134a-compatible filter-dryer

Upgrading the vehicle's radiator and radiator fan to give adequate airflow across the condenser

Pulling and holding a deep vacuum on the system, then charging it to the correct capacity with R134a.

Don't expect much out of the system unless you add significant insulation and window tint; vans like this what you're working on serve as very effective solar ovens and tend to overwhelm the A/C system's capacity to cool the interior down and keep it cool.

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Too many people who were born on third base actually believe they've hit a triple.

Thanks Dan! The windows are tinted and have curtains, and I have added insulation previously.

The van has a fan shroud and a five blade clutch fan, but I will see about swapping in a V-8 radiator from an A/C van.

I will look into upgrading parts, but I am trying to do this as cheap as possible. That's why I was excited to find someone with a nearly complete factory set-up. I still haven't seen the parts yet, but I will give them a thorough going over when I do.

If you have to do this on the cheap, then the place to spend money is on that parallel-flow condenser. A new filter-dryer is mandatory (not optional), too. You ought to be able to get a bigger/more-blades fan, a HD fan clutch, a fresher/juicier used compressor, and a fresher/juicier used H-valve from a late-model Mopar in a wrecking yard. The Nippondenso C171 compressor was used for a lot of years after the Slant-6/318 era — just pay attention to the mounting feet/ears, and the compatibility of the bolt-on hose fitting adaptors (if any). The clutch can be swapped (serpentine belt vs. V-belt). You may want to get some ideas on compressors via ebay searches.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

Thanks!