I just switched to corn last November, only put about 50 miles on before the driving season was done. I went from being able to run about 10 psi with a couple degrees of knock on real shitty 91, to 18 psi so far with no knock whatsoever. My chip is programmed for 21 psi and I'm pretty confident...
Did the bolts end up being metric or standard? I don't know how to spec the springs but those are shoulder bolts. Bolt Depot has a vast selection of fasteners in every grade and material you can think of, that is where I would check.
Sorry. I turned the resolution down on my camera as much as I could and the file is still too large for the server to process.... can't show you. The place I brought mine to did not have the equipment to do the original vertical heat pleats but they stitched them in and I think they look pretty...
Yes, I ordered 1 yard of the sand grey Brandon cloth from SMS upholstery for about 150 dollars and had a local shop upholster my existing door panels. They turned out pretty nice. Search "lear siegler bolster" in the hot air section and check out the thread on it.