Backing plate seal and stud tool question.

DMT lists 2 backing plate gaskets, both round, both with the same spindle/drum pic.
Both listed as having different size spindle holes, but outer diameter is not listed.

Original is that odd shape above.

I noticed on my spindle the surface shows circles from the machining process, as well as rust pits.
The foam gasket definitely held moisture against the spindle surface within the air pockets in the foam.

I was going to cut out gaskets from foam, as I have some, but now I'm thinking why recreate something that obviously failed and caused rust?

My understanding is the foam is there to prevent vibration noise, is this true?

If so, wouldn't it make more sense to use gasket material?

My 62 Dart uses the same foam material between the taillight housings and the body - and guess what, rust on both surfaces that matches the foam.
I was happy to find DMT makes these, now I'm thinking I'll make my own out of gasket material.

Mopar 66-72 Disc & Drum Brake Spindle to Backing Plate Gasket