I had to remove the lower bucket seat on the passenger side to chance the seat belts, to take a look for a possible short(which there was no electrics under there) and as soon as I put a socket on the rear four, they snapped right off. So, now I'm left with figuring out how to secure the seats.

And while I'm here, the pan itself feels ok, but there seems to be some sort of insulation or sound proofing that's cracked. How does that compare to the rest of cars out there?

Thoughts?

Oh. And what kind of glue can I use on the vinyl to reattached it to the bucket? Looks like some sort of brushed on rubbery cement was used and has long since given up adhesion.

That lifting "rubbery cement" tells me there's a lot of rust under it. It should be removed then the steel fixed / re-coated.

The seat mount doesn't look my 1973 car.

we weld new bolts onto the bracket. If you do not want to remove the bracket you can grind flat and tap

That's what i thought (grinding and tapping).

The rubbery cement was on the fiberglass buckets where the vinyl seperated from the bucket itself.

I've poked around under the car and cracked areas in the photos, and feels solid, but I'll give it a good once over before I put it all back together.

Thanks all!

The tar dries out and cracks but it doesn’t mean your pan is toast. An electric multi tool with a scraper blade makes short work of it if you want to remove and apply modern stuff.

I have other projects in the hopper...I've read dry ice also makes quick work of it (according to some Honda guys). I'm under the "if it isn't broke right now, don't fix it" mantra. The car needs way more stuff before that.
Probably gonna stay like that until winter.

Consider heat as being your best helper in this situation,mask and insulate the area and use a butane torch to heat the bolts ,apply suitable penetrating spray when they are still hot,you may need to repeat a few times.
Just use the very tip of the butane torch flame so you don't burn of too much paint,keep a wet rag near by to chill the area.
The longer broken ones will mostly unscrew with vicegrips the other ones you can be drilled out or if you have a mig welder and try applying blobs of weld on them so the vicegrips have something to bite on to.
If you don't have the skills or a welder you could just drill them out and put nut-serts in the ones that are broken off flush.
Good luck

when removing fasteners for the first time keep them penetrant wet for days prior to the work. Light tapping can help break the rust bond. Use a torque wrench set pretty low to try to loosen the fastener. Leaning in to it that last little bit with a wrench or socket usually results in failure. Be patient. The nut will be there tomorrow. What you will spend on dry ice will pay for a Rigid vibratory tool that comes with blades from HD. You can work at your own pace and will still have the tool tomorrow.

Thanks all.

Yes. I had soaked them with Pen. oil for a day, but they were too far gone. sure those bolts hadn't been turned in 48 years.

Good to know on the scraper. Are there any threads on sealing these areas?

Did you read my reply ?,NO penetrant is going to move these without heat this breaks the rust bind thats holding them and the penetrant can work .

Pen oil? What is that?

Penetrating oil = Pen Oil. I was on my tiny device replying an being lazy. Thought in the context of the thread, it would have been self evident.

I had soaked it prior to attempting removal..and prior to your post.

Thanks all! I'm gonna drill out the ones I can' get removed, tap and go. For now, that's my solve. I have too many other projects to get bogged down with these 4 bolts...I have a valve adjustment, new spark plugs/wires and roter and cap to install...and a brake flush....and a trans flush.