How do I get this stud out?
 

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Trying to figure out what that fitting is on top of that stud and if I can back it out of there to use the other stainless allen bolt like on the other side to finish up my extinguisher bracket. Tried some big pliers but couldn't budge it. Looks like an inverted Torx? The problem is I can only get that nut finger tight with how the clearance is.

Maybe these?

It's a external torx. Side note stainless tends to snap and you have effectively reduced the clamping force and connection strength of the seat/seatbelts to the truck. The stock nut is a flanged grade 10.9 for a reason.

What's a better replacement, Grade 8 hardware?

The grade you want is 10.9 because those are metric threads. Grade 10.9 is near equivalent to SAE grade 8.

I just used a small socket to remove the seat studs when I replaced my seats.

The grade for SS is like 1.5-2.0 (regular hardware store nuts and bolts are grade 2) and is designed for rust resisting, not for strength.

Okay I will see if I can find 10.9 hardware in M12 allen heads like the SS ones. Or Torx would work. I fully understand why the OEM's have to use grade 8 equivalent for these sorts of fasteners as a matter of safety regulations, but is there really a danger of a lower grade stainless steel bolt that is 1/2" thick not being able to anchor a seat belt buckle to a floor pan? That would be impressive if not.

The bolt is sized for crash loads which tend to be really high for fasteners.

Okay went onto Boltdepot.com and ordered a pair of 12.9 black oxide finish hex drive bolts that should fit in that tight space. Should also match the original hardware better.

Good choice on the 12.9 those will be perfect and far exceed the stock 10.9 strength.

McMaster Carr is also a good place as they carry pretty much everything and their website is easy to use. I just purchased some M8, M10 and M12 flanged nuts (grade 12.9). Make sure you buy zinc plated bolts & nuts as it will keep corrosion away (in most environments). Their prices tend to be on the high side but their inventory selection is unmatched and for $7 shipping they seem to ship everything next day air.

— Dave

A stop in a Harbor Freight and Fastenal got this done yesterday. Fastenal had the 12.9 Hex drive bolts (M12x1.75x35mm) and HF had the external torx sockets to get the stud out. (It was an E11 size)

Pretty pleased with how it turned out actually. I did have to use a round rat-tail file to slightly enlarge the two big holes on the bracket, and obviously the stock bolts are too big, but the new ones fit in the recess area with a mm or two to spare.

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