If you have your seats recovered all the old material will be replaced so ... no odor.
Even without seat belts I think the 1965 should still have the nuts welded to the floors so lap belts could have been installed as an accessory.
I don't know if I still have my measurements but for the top attach points I just drilled a hole with a taper bit (1/2 inch I think) and then used the backing plate that comes with one of the hardware kits. I was ready to use a wrench on it but it tightened down just fine without a wrench.
