I've been reading the many threads on replacing then OBS MC with a NBS MC and have decided to take the plunge. So here is my question. Went to AutoZone and found four different MC listed for the 2004 Tahoe. Two hydro boost and two vacuum boost units. They also list different brake equipment options. So if you are going to buy a NBS MC for your 98 Tahoe does it make a difference which one of the four you get or will any of them work? Thanks.