This is a complete Top End offered by Cat for the 1972 EXT290 to run in MOD class.  (It also can be used on all Kawasaki 290/295 T1A/B powered Arctic Cats 1971-74 like the El Tigre' 250, 295, 340).  It is the optional MOD kit that was offered at the time. . Was intended for Racing, as outlined in the commonly found Racing manuals. Those manuals have all the set-up information needed.  This set-up has the correct OEM New Mod single ring pistons included. I also have more Mod OEM replacement rings for this set-up available. And I have the intake blocks and carb flanges.(uses stock El Tigre' intakes)  (Designed to use 36mm carbs).  There is one shallow groove in the Mag cylinder. It just barely can be felt. Otherwise everything else shows virtually flawless for used. There is no Porting changes done to any of the transfer or exhaust ports. There is some very mild smoothing of the intake with no actual porting changes.  I am including (2) NEW Correct Mod pistons and rings and (6) NEW replacement OEM single rings for the Mod pistons. Also I am including (2) USED Oem Mod pistons.  Both usable, one good, one 'fair'.