340 LA one piece pan gas gasket

The later one works, but you have to squeeze a bunch of goop in the corners due to the LA pan having a notch and the Magnum one piece gasket not having the same notch. So the later gasket doesn’t seal at the corners if you don’t take it into account.

That's exactly what I've been running for years. Works great. No leaks, and I tend to get 2-3 uses from them if I don't break it during removal.