My dad has a 1998 Suburban 1/2 with 130K and original shocks. While towing the 27' snowmobile trailer the rear wants to bob up and down a little on bad, bumpy roads. What shock is basically the best out there? A shock that will help combat the up and down bobbing while towing but also not stiffen up the suspension too much when not in tow is desired. We were looking at the RS5000 Rancho and Pro Comp ES3000's, are the adjustable shocks really worth it? Thanks guys!