I would stick with behr, but I've used an acm for an evaporator before with good results. A properly charged r12 system on a w126 is actually pretty good. I wouldn't bother switching out condensors, I doubt it will be worth all that extra headache.

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Eugene

10 E63 AMG
93 300te 4matic
07 BMW X3
14 Ford F-150 Fx2