I used two thick pieces of rubber cut from an old bedmat, one under each side of the stock battery clamp. Total of four pieces for both batteries. This has worked fine for almost 2 years now and never vibrates loose.
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Ron
'96 Club Cab 2500 4x4, 4:10LS, Auto, BD Pressure Loc, Mystery Switch,TST 230/605, Cummins Chrome, Mag-Hytec rear and trans covers, Boost, Pyro and trans gauges, Optima Red Tops, All black. Tow 14k HitchHiker triple glide 5th Whl. Also use 9. 5' Lance. NRA Life Member.