lead weight or sand bags

A wholesale plumbing supply should sell lead bars. I fabed metal boxes that were open on top and had a strap that clamped them to the back bar of the roll cage. There were three on each side and could be removed one piece at a time to obtain the proper weight. All total we used to run about 400 lbs in the trunk. It definitly needs to be bolted in. Rolled a car at the strip on time, if that lead had come lose, just no tellin? Hope that helps