New panels advice
 

I have an 85 2+2 5 speed 300zx... love the car.

However, there's some rust... the rear subframe mounts have 3 bolts on each side. one large 17mm, and 2 smaller 14mm. The 14mm bolts go through the floor pans, while the 17mm bolts to the chassis. Well 276,000 miles later, the floor pan rusted completely through. Both sides seem to sag into the floor.

How should I properly fix the panel?

What I was thinking of doing was jacking the car up so its NO stress on the subframe assembly, and then welding my own panels in from there. Good idea?

Picture.

http://farm4.staticflickr.com/3788/1...26d83a4b_z.jpg
http://www.flickr.com/photos/89863793@N07/13321565313/]Untitled[/url, on Flickr

Find a donor car if you can
 

Depends on your fab skills I'd say, if you could cut the floor section out of a donor car you could cut and replace, looks like some welding and cutting is needed. The big trick I'd say, is if is sagging, getting it level when you weld it up, perhaps a few braces once you get it square, the tack brace it, weld in your panels and then remove the braces. The FSM contains a body alignment chart, with it you can get it exactly where you need to and verify it.

I made my own frame rails for the car, so I'm learning. I'm also making rear quarters, and sections of the rocker panel. This seems to be the hardest though, because of the curves.

Ultimately I need to just go look, but could you, or someone, explain how I can get both sides within proper alignment spec? How do I measure that properly?