Can't help much with seats, There was a thread on this site about newer f body seats that installed well, I would think that almost any bucket could be adapted without too much trouble.
RE the tags, repop trim tags available, but most are going to be spotted, and may raise questions about the authenticity especially if you have a more desirable model, or options.
You are not allowed to replace the VIN tag, that would be a federal offense.
Tom