I'm trying to install a RDS Aluminum combo fuel/tool box that was given to me. Originally, it was used as a gravity fill and had a large elbow neck welded on the bottom which was not good to say the least. I had the bottom drain cut off and welded. I'd like to do this right but it seems I may need to buy the installation kit for $240. 00. I thought I might be able to do it for less $$$ but I don't want to take any chances... got any suggestions??