Mine is a long story and "ain't over" yet. I originally was going to adapt later model Sanden to the engine from an OEM engine, but the brackets are huge and ridiculous, and then buy a "hang on" under dash unit off ebay
Things changed. "Fratzog_Lover" ended up selling me an AFTERMARKET underhood lot that he removed from his car. this is "all the stuff" that hooks to OEM AC but uses an Sanden instead of the old Mopar cast iron pump
http://www.forabodiesonly.com/mopar/showthread.php?t=322104
Then, in the midst of that, I ran into a local guy with an "almost complete" Vintage Air kit
In the photo below, the firewall side of the unit is at the bottom of the photo. The two round holes connect to your defroster outlets. The three oval fittings are A/C outlets, and "you can't see" the heat floor outlet out the bottom of the unit
The only downside ? is that there is no provision for fresh air, and you'd have to "do something" with your original fresh air cowl fitting. Some guys claim you can adapt a driver side fresh air box. Look at the thread I posted. I may adapt a Mustang air box as I did for the drivers side.
This very quickly changed "my direction."
This is similar to what was posted above. This is a complete, self contained heat / defrost / under dash unit, that requires NO firewall entrances. In other words you can re-route the heater and AC lines out to the wheel well to hide them better. I will probably use the factory heater hose openings in my (non AC) firewall.
This unit is VERY compact, and you can look up the specs at Vintage Air
This box is called a 68000-VUZ-A is known as a "ComPac Gen H W/DEF" and if you Google that you'll find "stuff" on it
Size of unit from Summit:
As you can see it's VERY small
http://www.summitracing.com/parts/vta-68000-vuz-a
Thing is you can buy these units separate if you want. They are very small, and integrated heat/ defrost / AC
Downside as I see it:
Not "resto correct"
Smaller, may not output as much heat. I won't be driving mine when that cold, anyhow
No fresh air. It is 100% recirculate. I may hack up a vent box
UPside
For me, a "deal" made this cheap
All set up for modern 134A
New components instead of 40-50 year old components
Much smaller and lighter
Might be able to better hide hoses, out in fender, etc.