The key area is your inner rockers (and torque box), if they rot your car will start to fold, the top of your door will start to overlap the top of the quarter. Mine hadn't folded but I was running on borrowed time, as you can see what was supposed to be a complete box is down to an inverted "U"
Well I see that you're in Texas, that helps a lot, I'm in the Pacific Northwest rustbelt where mustangs truly are rustangs
There is no rust you know of...I'll see if I have the pictures on photobucket...what 65Rob said is exactly what you need to look for. WHat does the car do on a lift? Watch the gap at the top of the doors to the qtr panel. THe 71 we did had to have a RH rocker. THere is the outer rocker and an inner rocker with a plate sandwiched between them the whole length of the rocker. When I pried the fist sized ball of goop out of the rocker at the rear wheel well, (they had put a plate over the rusted hole and pop rivited it on...) I could see up the whole length of the rocker. THe plate had completly rusted away inside the rocker due to a cowl leak. The inner and outer were fine, but the gap on the RH door opened and closed nearly an inch! So we knew something was wrong. I'll edit the post if I have the pictures online.
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OK, I don't see the detail pictures of the RH side. Not sure whats up with that...you can see the repair I made to the LH side, and can see where I cut the outer section off, cut the rust from the center plate, repaired the inner, repaired the plate, reattached the outer...the LH side was on t;s way to looking like the RH side. I ran the shop vac hose up the inside of the RH rocker to clean it out. It didn't immediatly dawn on me that the entire center plate was GONE and the debris was what was left of it...so it had to come out.
Anyway, check the car on a lift and see how much the gap changes. I bet it hardly moves and you can sleep at night again!
Image hosting, free photo sharing & video sharing at Photobucket
OK, I don't see the detail pictures of the RH side. Not sure whats up with that...you can see the repair I made to the LH side, and can see where I cut the outer section off, cut the rust from the center plate, repaired the inner, repaired the plate, reattached the outer...the LH side was on t;s way to looking like the RH side. I ran the shop vac hose up the inside of the RH rocker to clean it out. It didn't immediatly dawn on me that the entire center plate was GONE and the debris was what was left of it...so it had to come out.
Anyway, check the car on a lift and see how much the gap changes. I bet it hardly moves and you can sleep at night again!