Finding a close fight for Naruto in American comics isn't easy. The guy tends to have too many powers, but his strength and speed cap too low to jump up a whole weight class. Iron Man has been my best guess lately, but I haven't read as much of him as I'd really need to be sure.
Round 1: Naruto with all feats, including 6 paths mode VS Stark in his most current everyday armor.
Round 2: Current Naruto and Sasuke VS Stark plus whatever he can reasonably summon mid-fight.