Craig,
Fortunately the aftermarket now provides a source for these pieces, but if it were up to me I'd try and source a set of factory panels. I have no experience with the aftermarket FG interior pieces, but what I do know is that the original pieces fit "like a glove" and there isn't much room for a margin of error. If the aftermarket new ABS interior pieces are anything like an aftermarket hood/door/fender/etc. you'll likely regret using them.
It's a rare occurance, but original FB FG interior pieces do appear on eBay now and then, just be prepared to pay for them. It would have been better if you'd started looking a year ago.....