Upper Door Hinge Captured Nut Stripped - HELP

70 Roadrunner & I stripped the captured nut for the upper door hinge on the driver's side. If it were one of the two bolts coming out into the hinge, I would just replace the hinge, but is the bolt that has the captured nut up in the body.

How do I fix it? Where can I find another captured nut?

I've considered two options.
a. replace the nut (if I can get to it & if I can find one)
b. take off the door and see if I can tap the hole a little larger, maybe metric, and find a different body bolt with the "guiding nose" on it.

So what do you guys think? THANK YOU

I'm thinking you will have to take the door off, an you should be able to just retap it I would think.

Yeah, I think you're right, but a guy on FBBO suggested maybe trying a slightly longer 3/8" bolt first, so what the heck. I was putting in a 2nd 1/8" body shim at the time...so maybe I have some threads left.

If worse comes to worse.....what is up in that cowl area? (captured nut? threaded plate?) and how do I get it out?

Just to be clear, this is the top driver's door hinge...the half that bolts to the body. There are two bolts coming from the interior area into the hinge from the inside, and one bolt coming from the outside into the interior area....that's the one I stripped....otherwise I'd just repair/replace the top hinge... the stripped threads are up inside the interior/body/a-pillar/cowl area.

I really don`t know what room there is but I would use a longer bolt and put a nut on the backside if it is accessible.

Due to the inaccessible nature of the plate, start with the smallest repair possible. In this case, a longer bolt might work.

Next step, tap it for 10mm threads. I'd go 10*1.25.

If that doesn't hold, a 3/8" heli coil can be installed.

Thanks for your help everyone, I got it. I was able to snake a 3/8" tap into the door/fender crease & turn it in with a pair of small vise grips. I then used a 1-1/4" 3/8" bolt with threads all the way down & it tightened right up. THANK YOU