Since you used the word "retrofit" I assume either you weren't thinking of using a factory system, or you are asking about retrofitting an R12 to R134... in my junkyards 2nd gen's with AC are kinda rare, 1st gen's with AC are really rare.
If you just can't find a donor (I think I would buy a complete roller off facebook marketplace, etc), then you could also do what the antique crowd does - magic aire, etc aftermarket mfg. who made em in the 60's (when AC first became available at all) to go into 40's and 50's and even 60's ones that didn't come with factory (which was a super top of the line 'deluxe' trim).
And since we are talking 1st and 2nd those are gonna be pre r134, so like ?R12? that will need to be retrofitted, which means changing all the O rings everywhere, etc etc - there is an article in the tech library. The first one is more just covering all basics, but includes more R12 stuff, the 2nd one is specific to 1994, but talks a lot about retrofitting R12 (Author claims that it was near 1994 when the switch from R12 to R134 happened, which jives with my memory too).
BY Michael A. K. Gross, Ph.D. Now that it’s nearly summer, lots of people are dusting off the old air conditioner, and in some cases unhappily finding out that it isn’t cold. This article describes operation, basic service, and … Continued
www.therangerstation.com
Its summer and your A/C does not work. That sucks. Well, I have the write up to help you get it back on the road. Keep in mind, my write up only covers 134a systems, specifically in the 1997 … Continued
www.therangerstation.com
Ultimately, even though I am headed to Austin with my ranger, I am not gonna bother because it is a holy crap load of work, but I read all about it before I decided not to.
You wont find an AC service company that will reclaim your R12, but you might be able to get a junkyard to reclaim out all your R12 from a roller/donor as a service.