Ok 86560SEL now maybe I can give you a better answer, this is coming from my ongoing W126 project and from people I have talked to. W126's are awsome cars, I think one of the best ever made they drive great have awsome brakes and in the 560 trim haul ^*^! Not to mention the very high build quality, and the fact that they are simple to fix. Now the downsides they are not cheap, if you buy a $3k W126 I don't care what model expect to put $3k into it in the first year or two if you want a real nice car. These cars require constant attention you always have to be on top of them, however as I am finding out once something is fixed it tends to stay that way for a very, very long time. You really have to want a W126 to own one at this point in their lives. Their getting to be old cars and will need a lot of work to keep them on the road. The newest W126 is a 1991 so 13 years and around 130k miles with normal use. If you want a problem free W126 that you could just drive them look for a perfect early 90's one, these seem to go for $10k-$15k, but you will have a mint car with all of the service up to date. $3k W126's will need work unless you get a killer deal. However now that I said that, model choice has a lot to do with how much money you will spend.

Figure 420/560SEL's to be about the same to run, both big V8's 560's probably have more features although not always true.

300SDL's/ 350SDL/SD-are great but they didn't make many of them so some 603/SDL specific parts are big$$$(think radiator $395/ Oil cooler+lines $650) Not to mention that 350's hold their value, try finding a nice one for under $8k, and the well known rod bending issue.

300SEL's are nice some people say their slow, but I think the W126 is a great car for an inline engine(this includes the above SDL) Their is a lot of room under the hood with the six's.

The 300SD is probably the cheapist one to run, the 617 seems to have no weak points, other than it is a loud, slow, diesel. (not a bad thing!)

Then you get to the pre 85 W126's/ 380SEL/500SEL, I don't know much about these other than the 380 had a bad single row timeing chain. The 500's seem to be nice cars.

My advice is the forget about the mileage and year and just buy the nicest one, look for one with a lot of recent work. That means you will have to do less updating yourself.
A few major points:

Rust, rust, rust, it is a cancer and will kill the car. I would pay a lot more for a true rust free car. (Look for my W126 post in the diesel forum, I outlined the trouble areas)

Don't buy a $3k W126 unless you can/plan to put $3k into it, look at it this way it will be better than a $6k car when your done.

Condition and service records, the more records the better, same with condition.

Be ready to work on them yourself, it would cost way to much to pay someone to do everything. (at least in my view)

Other than that their great cars, and yes it is worth it.

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