The earlier models had smaller underbody panels - quick google can show you:
https://www.ft86club.com/forums/showthread.php?t=38946
Scroll down to see the USDM vs JDM underpanels
Looks like you can buy the kit still, I think you save a few bucks ordering them yourself though
https://www.ftspeed.com/part/86-unde...ro-underpanels