you can buy brand new evap with a standard TVX, not cheap (300ish iirc) that is a drop in replacement. I would go with a parallel flow condenser (pick a genereric size that approximates the oe size and rig up some mount hardware) a SD709 and a generic drier, then use the new evap in an OE housing. Using the PF condenser should allow for good use of R134a vs R12. I got my new evap just in case my old one leaks or the tvx ever looses its charge. At that time I would just swap out the evap and stay with R12 since I have a good condenser (was a NOS unit). I prefer the old hitachi SWP types with the sump, they are heavy as a tank but cant argue with longevity (looks OE on mine and runs fine). But the SD709 is prob a better choice if you have the mounting bracket. It prob works better (quiet, light weight), but I always wonder about the quality of stuff like this. I think there maybe some other tweeks if you car did not come with AC as far as making it work, its all covered in the FSM on how to add.
Often see the entire AC system for sale on eBay, a good way to get all the pieces then if the evap is bad just replace it with the new one I mentioned above.