To equip your sherman with an airsoft unit you'll need parts from the new VS Tiger I tank in 1/24 scale. The airsoft unit, barrel elevation unit, turret ring and turret rotation unit. All very compact and should easily fit. I've scoped the parts out, and like you haven't bought anything yet. You can get them from Toyeast for minimal cost, less then $60 shipped. Get a spare airsoft unit while you're at it.

While you're saving for the Sherman why don't you pick up a Pershing or Tiger tank in the meantime? Find out if the hobby is something you'll enjoy before spending the big bucks! And don't worry, Nobody who's visited this forum for more then a couple of months owns just one tank anyway!