I wouldn't focus on the Sanden too much. I put that in my 1985 and can't say it cools any better than my 1984 w/ original R4. Both use Duracool. They are both fine at what is considered "very hot" in the east (93 F), but barely acceptable on our >100 F days. The air coming out the vents is still cool, but can't keep up with the heat load, especially if driving into the sun. Of course, worst is when sitting in traffic and the electric fan doesn't quite keep the condenser cool enough. On the highway it seems OK. I even tinted side and back windows in the 1985. I did use a Sanden "shorty" (H13), so an H15 or 508 might do better, I don't think they would fit the way I re-used the factory hoses. I suspect a parallel-flow condenser would give more bang, but is a custom design.

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1984 & 1985 CA 300D's
1964 & 65 Mopar's - Valiant, Dart, Newport
1996 & 2002 Chrysler minivans