'63 Valiant V200 wagon - rare bolt issue

@shortmort37, I agree with @RustyRatRod, tap the hole. You said you didn't have room, can you provide a picture? Now I have NOT seen it yet, but it seems that if you can get the bolt and a wrench in the correct area, you should be able to get a tap in there. If the area is like inside the tailgate and there is no room to use a standard 1/4 x 20 tap, then try to find a short/stubby tap or make one. If necessary, I see no reason why you couldn't cut a regular tap shorter and grind a square top on it like on the top of a regular tap. That is what I would do.