As a preventive measure, I'm planning to replace my radiator. I understand the old ones tend to crack at the necks eventually. I'm going to do whatever it takes to avoid over-heating the engine and the "delicate" aluminum head.
1) What's a good source? Dealer wants $470 - I'd like
to spend $250 - $300

Get in touch with Phil here at fastlane/partsshop.com They have good prices on MB radiators and it also helps support this site.

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Jim

Having just gone through this replacement with my 1983 300D (287,000 on the clock) because of a broken nipple, I can do nothing but praise Phil for his support and help in the replacement.

Phil was able to locale the radiator here on the west coast and was in the car the next day. I did replace all the trans fluid and filter with Mobile1 synthetic and she seems to be shifting MUCH better.

Thanks to this site and all the many fine people who give their support and knowledge.