Resuming the day 439 runs behind, opener and comeback man Gugale slammed 154 with 28 fours, while No 3 batsman Khurana played a perfect ally with an equally delightful 125 (13x4) as the duo stitched together 270 in 469 balls for the second wicket to curtail the deficit.
Ankeet Bawne, unbeaten on 47 (9x4), and captain Rohit Motwani (4*) were at the crease with Maharashtra 394/5 at stumps, trailing Tamil Nadu by 155 runs.
In reply to the massive 549 by Tamil Nadu, Maharashtra batsmen showed fine temperament and with little assistance for the bowlers from the Eden surface, it was a chance worth taking.
Earlier in the morning, Gugale and Khurana showed the way as the overnight duo carried forward from where they left and never looked in trouble against the Tamil Nadu bowlers.
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Gugale, who was dropped after making first class debut against Rajasthan in 2010-11, continued his fine form this season as he got to his second century by slicing Aswin Crist through third man boundary in the morning session.
"I always dreamt of scoring a century at the Eden Gardens. I will always cherish this moment," Gugale said.
It was a perfect start for Maharashtra who scored 119 runs from 31 overs in the first session without losing any wicket.
Khurana followed his opening partner by getting to his fourth first-class century when he straight drove Aswin for a single after lunch.
Gugale lost his patience momentarily when he tried to pull offspinner Baba Aparajith, but could not clear Laxmipathy Balaji at deep midwicket 20 overs.