LRG pretty much covered it. Engines prior to the break point really should have the dam gasket, but the problem is finding one to install. You can find your engine number on top of the block, behind the main fuel filter, or decode it from the VIN using the EPC. That will confirm if you have an early engine or not. Very few engines fall into this category though. At the moment I still don't have a source for new dam gaskets.
If you install a dam gasket with the basket in place, the pump won't seat, as the dam hits one of the basket mounting bolts. If you started the engine it would dump oil all over the place. It's fine to leave the basket in there if you want, on a later engine, with an outline gasket.
Anyway - I fixed the link in the earlier post (thanks for letting me know!). Here's the link again to the PDF with more details:
http://www.w124performance.com/docs/mb/OM60X/OM603_vac_pump_mod.pdf
