The front guards are completely different, and the rear quarter panels have big sections cut out of them to accomodate the guard extensions.
Apparently it's possible to purchase a body kit which mimics the MA61, some bloke from the Gold Coast told me about it when I was getting one of my guard extensions repaired after a close encounter with a concrete pillar. So maybe that would be worth investigating if you want your Celica to look like a Supra.
Or, you could just buy a Supra and be done with it.