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The previous owner butchered the bolt threaded mount welded into the firewall.  I have tried unsuccessfully to save it by rethreading it out to a larger size.  Thinking of drilling through the firewall and placing a permanent nut on the backside of the firewall.  Problem is the gas tank (this is s/n 744) wrapped in fiberglass sits flush against the firewall.  Has anyone undone the metal strap that holds the gas tank and moved it backward to allow access to the backside of the firewall?  If I can gain access, I will drill through and JB Weld a nut into the firewall allowing me the ability to finally secure the upper bolt.  Dont want to attempt to cut the threaded tube out and replace.  That seems difficult.

Original Post

That bolt is a stepped shoulder bolt to allow the upper seat belt mount to rotate. I've removed the tank strap and shuffled the tank back for access successfully in the past.

Seat belt bolts are pretty much universally 7/16-20 UNF, if it were me I'd drill out the existing hole get some tubing to slide in, weld up and tap a new thread. 

6B68CF35-DB83-4407-A1B0-AA9DC38DB0842511 was set up by Dennis Quella for a shoulder harness with a single attachment point. He added a vertical U-channel to the steel firewall which included the new anchor point. 

I found that anchor point to be too low, so it did not properly thread through the harness hole in the top of my Recaro seats. 

Using 3/16” steel plate, tubing and a nut, a new anchor point was fabricated. A clearance hole was then drilled in the top beam of the firewall and the plate welded in place. 

If you have the ability or access to the welding skills for this approach, I believe it would serve your purposes quite satisfactorily and be much easier and more permanent then fighting with a gas tank and using JB Weld. 

Larry

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We've fixed a bunch of them. Don't trust you life on helicoil or epoxy. Simple fix: Push out your rear quarter window real quick, slide a piece of flat steel around where you think the hole is, drill it out all the way through. You will not touch the tip/edge of the fuel tank if you're careful, it's lower than you think. Safety first, slide a slab of steel for safety & drill away as afore mentioned. Apply any nut/bolt configuration your little heart desires. We use a thick 3" large seat belt washer on the fuel tank side. It'll NEVER come'a'loose. Replace the glass using a piece of rope. Quick job no big deal.

Shark

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