I would agree on all the previous posts . I would only do full otrs. As far as nos parts they are great if you can find them but they are getting hard to find and very pricey.It depends on if your restoring a all original copo,z28 your in your best interest to put as much nos stuff as you can find to keep the value of car up. I have installed dynacorn 1-piece trunk floor,complete floor,upper cowl,sidecowls and fit hasn't been that bad.You'll need to do some trimming to make fit but that comes with the job.I've also used some of the usa inner+outer rear wheelhouses ,rockers,upper dash from heartbeatcity and they are really nice .Good Luck let us know how you make out.
Joe