What I suggest is if You want to stay with Simplicity any of the Current Models can take the Turbo wide Body cart and several Older models as well which has caster wheels and the Cart stay straight in line with the tractor or any Deere since the Mid 1990's LX100,LX200 ect the STX and LT100 series are the Only tractors That won't except the MC519 Cart But even JRCO makes a Universal Mounting version of the MC519 Cart http://www.jrcoinc.com/moreprod_detail_cart.asp I think either of those Carts will Cover Your Need for a Built In wagon I believe they are Both Made By JRCO anyways:thThumbsU