Has anyone used these with good luck? Seams as though Performance-seal handles them. I don't know the manufacture which would tell us material?

I have not heard good things about these. Very difficult to install correctly -- you've got to cut the seal to install it -- so it's really not a one piece deal after doing that to it..........

What if you have the crank out while you're installing it?

You cannot get the seal over the rear crankshaft flange -- the instructions state you need to cut it to install it. You would be installing this when the crank is out no matter what.

I found that Pontiac has a one piece seal for their engines 400 and 455. the seal comes marked to show cut location, (between the wire re-inforcement). Users find it easy to install and leak free! This seal must be similar to the one piece mopar, and still looking for the maker?

Even with a cut it still has one less spot to leak. ???

We use one piece crank seals on airplanes, and they work fine. We heat them a little, and take the spring out, and there is a special tool that strechs it over the flange.