It realy sucks to pay someone to make mistakes and mess up your vehicle. I would surely have thrown this problem back on them and made the at least order the correct bolts from Mercedes.

I think the issues is going to be more what grade the bolts are supposed to be. I know that compared to the other typical grade 5 bolts on my Van the Flex Plate bolts were grade 8 washer head bolts with a locking coating on them.

When I look in eBay for "1984 Mercedes Flex Plate Bolts" I see a pic of a regular looing bolt with some sort of locking coating on it.
Part number 054 33017 001

The same search brings up what appears to be the Flywheel Bolts mislabled as flex plate bolts with a different part number.

__________________
84 300D, 82 Volvo 244Gl Diesel