No, I don't think it's absolutely needed but leaving it off would expose the flywheel a bit on both sides of the block. I don't plan on any diesel or oil leaks but who does. Besides, in any engine bay there must be some significant air swirling about (especially at 100 MPH

), and should a leak happen, slippery stuff might end up getting in there.
I figure Keeping the flywheel clean is a great way to keep the clutch from slipping.
One of the things I noticed though is the "0" timing mark on the (non-stock) flywheel is not in the correct place - not even close. I won't know the "correct" spot till I slip the tranny on and set it to TDC based on the arrow on the bell housing. I may buff out the current mark so there's no confusion.