I can get Bosch plugs in boxes of 10 each. Almost anything you need. W7DC are readily available but I use W9DC on all engines except those that have full compression and rebuilt injection pumps.
Most of these engines run too rich and W7DC plugs realy are not hot enough for most cars.
Dan Caron's
SL Barn
benzbarn@ebtech.net
slbarn.mbz.org
1 877 661 6061