Denis, I think Wesley's Bleche White was developed back in the days of wide-whitewall tires. Don't know why they would spell it "Bleche" though--perhaps the word "bleach" was already copyrighted by another company, maybe Clorox? But I digress... Bleche White is fairly caustic stuff and the product label indicates that it's only use is for tire care. It also cautions not to let it contact "magnesium or aluminum wheels, painted or glass surfaces, eyewear, fabric and non-rubber items. Permanent damgage can occur." Sounds like it could eat vinyl seat covers. I can attest that it works wonders on tires though.
By the way, your Deepwater '67 Z is breathtaking. I looked it over at the Chevy show yesterday and I might have drooled on the fender--sorry. You also need to send pix to Belair. Oh, and your "Granny's car" '67 RS/SS 350 is a real time capsule. Don't change a thing.