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There are ONLY 2-AC 'Kits' suitable for an M800 - one is the Subros' that comes as an OE fitment and the other is the after market 'Sanden'. The rest/cheaper wayside ones are mostly 'mix n (mis) match' and as such, they seldom work satisfactorily, if not kill the engine sooner than later by overloading it. Besides, all car AC's can rob a car of 10-20% of its power and associated fuel consumption - for obvious reasons.
Will cost you around INR 18000/-.