Gai takes him down in S1 considering how he was able to put Juudara at the edge in CQC. KCM Naruto won't blitz or at last keep up with Gai since BSM Naruto had trouble hitting Juubito, who was far faster than KCM. He offense also won't be of any help since Gai can stop him dead on his track before doing anything. Then there is simply Hirudora being able to pummel KCM Naruto since it can take out Madara's V3 Susanoo.
Naruto can win S2 by first placing up clones with the same reaction levels of KCM + SM. KCSM Naruto is almost the same as BSM Naruto without the heavy hitting offense and slightly slower than BSM. Multiply that by the number of clones and Gai will have a harder time keeping him down. They then can follow through strategies like the ones used against Third Raikage and Pain. If this KCSM Naruto refers to The Last Naruto, then he honestly takes 7th Gates Gai down very bad.
