I guess my explanation wasn't understood, so I'll give it another shot with some pictures. The distributor on a 4 liter engine can have the problem where the flange intended to stop it's rotation can break off. This has nothing to do with the distributor not going in far enough or poor manufacture - the problem resides with the block itself. When the distributor is fully inserted, the flange I'm describing, doesn't come down flush with where you'd expect it to be in order to bolt it down and this is because that part of the casting is LOWER than where the neck of the distributor fits in. I don't have any pictures of the block to show you, but the pictures of the distributors should give you a good indication of what I'm describing.
First, here's a picture of three different distributors, one is from the new variety of I6 that has no cap & is for the cam sensor only - here you can see that they no longer even have the flange. The other two are of the same configuration, but one has the flange broken.
Here's a closer picture of the flange:
And, here's a picture of the hold-down (clamp in my previous description) you need to solve the breakage problem:
Here's a picture of a bolt sitting on top of the flange - you can see that it's not machined for the bolt to provide even pressure:
Here's a picture of the hold down positioned properly to pull the distributor tight against it's mating surface & the bolt also positions the distributor correctly but doesn't put any pressure on the flange - no breakage. The bolt in this picture is obviously too short, I just happened to have it handy for the picture.
Here's one more from a different view:
I hope this proves to be helpful - the distributor with the broken flange is one that I broke before discovering how to deal with this problem. Some lessons can be costly, thankfully, I had several spares.