Relace washers with usual flat steel washers...or stainless if you can find them.
The 80' 116 and 117 engines used aluminum cam covers , and yes, they warp too.
The 560 was a 117 block and heads should size out same as 450 .
Check with your local parts recycling yard.
There will be others here that have, btdt.
BTW, the copper washers MB used, were to stop oil leaking out of bolt bosses and give a soft seat for bolt head/cover interface, instead of directly onto cam cover boss.
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