The idea of hacking up the firewall gives me chills.
I've done a couple of fan replacements in W114/W115 cars. Both had AC. Typically it's a take it apart on the first day, put it back together the next, job. New fans are getting expensive now. the last one I got, for a '72 220, cost over $300! A friend gave me a NOS fan he had bought for one of his now-departed 220Ds. I'm saving it for my 250C. Many years ago, I did a heater R+R on a non-AC 220SE Fintail and don't remember it being that hard. I assumed the W108 would be similar, except for the AC in the way, but I could be mistaken - haven't done one of those yet. The original heater and fan in my '60 Fintail is still working. Good luck with yours.

Happy Motoring, Mark

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