I've called Benz friends and all they have are engines that are good for cores.
I can't justify paying for a reman'd engine for a car that isn't worth that much. If it were a car with sentimental value or it was still worth a 1/3 what it originally sold for that sure I'd buy a motor from MM.
I've called around machine shops. One place quoted the head could be done for around $125 but I'm a bit dubious about their quality. Others averaged around $400. The block is another story. Few wanted to even mess with it. The few that would try, (the word "try" bothers me), quoted around $500 to do it and I would have to supply the sleeves. Chances are I would need new pistons in the process and we know how much they run.
I talked to the shop that is famous for working on Mercedes in Portland and they said they don't rebuild many 617's any more due to the high costs involved.