After struggling with the replacement PCV grommets that are pure hell to install because they fit so tightly and the groove is smaller than the thickness of the manifold (at least on an SP-1), I staggered in to the local Car Quest Automotive place and checked out their fine selection of quality Chinese grommets. Came across the HELP! number 42049 that's for Ford/Mercury 75 - 94. It has a wider groove, it's more flexible, but is still about a .200 interference fit into the manifold at the groove. The stock PCV goes in tight, but not a beat it in with an 11/16 deep socket and a hammer. From what I've seen, most of the stock grommets are so tight around the PCV you can only get the PCV in about half way before you get nervous about driving the whole thing, grommet and all, into the valley. Anyway, for what it's worth, and your mileage may vary.
Pricey but were recently available. I bought a few and I always spray a little silicone on the pcv to help it slde in.
