Yes. Timing chain problems are just as common on the 560 as the 420. They are both V-8s. There is not a lot of problems with the chains breaking, but with the guides (plastic) becoming brittle and snapping off. The piece then gets lodged between the chain and sprocket and causes the engine to "jump time" which causes the valves to come into contact with the piston(s).

I would seriously consider the '90 420. Not only are the miles lower but it has a complete service history. Most people who bother with keeping the service history take very good care of their cars. You can also see what was done to the vehicle ie: timing chain. If it was done already you have an extra $1500 in which you didn't have to spend on that job. Also, the 420 does not have the hydraulic rear suspension to deal with. On a recent trip to Georgia I got 23 mpg with mine with 4 adults and luggage - going 70-75. Around town is not so good but I average about 17-18 mpg.