The latest DCS version is 4.30 and the latest hardware are the kits with the Rev. L.
I would strongly suggest that you purchase only a DCS kit (or separete-sale TIU) that has a Rev. L included. The Rev. l, in its current implementation, is far superior to any previous TIU.
Further, it would be wise to purchase only a new set (or TIU) and only through an MTH-authorized dealer.