Injector seals are commonly available.

I only know of plastic shields for splined lockrings. I've never seen one for a slotted lockring. Shields for splined lockrings are no longer available. EPC says it's okay to go without. You'll have to ask Phil (Buy Parts link at the top of the page) if anything's available for your car.

The shields I'm familiar with engage the splines in the lockring. In fact the splines clock them. They slip onto the lockring then the injectors go on.

Sixto
93 300SD