[Mr.Black90]

How big are the holes?
If it's not crazy bad maybe you can use JB weld that can be used in gas tanks.
I hope this helps.

It's big enough that I can get my hand through it. I'd say a good 3rd of it is gone. I'll try to get pictures tomorrow.

 

[Mr.Black90]

Is it just the sheet metal around the filler neck or is it the filler neck?

I noticed on my 99 that it was rusting through just below the filler neck. I treated snd painted it. I took out the rear speakers and found lots of rust inside the cavity there. I treated that too. I think the filler neck is probably a separate piece that sits inside that body metal. I guess I could look up a parts diagram from the manual but no need since it’s intact.

It's just the steel around the neck. But it's completely rotted through. I'd need to cut out a good chunk to stop the rust. I was hoping that there might be something like a drop in piece I could patch into it or rivet in place instead of attempting fiberglass or welding around a gas pipe. But the only things I've found that are along those lines are for jeeps and fords. I was thinking I might be able to modify a Ford one to drop in after cutting out the rot.