After reviewing the options from American Classic, Chevy Duty, LMC and Jim Carter I admit to being confused on just what inner cab corner I need for my 54 3100. American Classics has one that is 6 inches tall while the others appear to be 4 inches. Are the 4 inchers meant to be spliced into the existing remains and the 6 incher a total replacement? The American Classic is the least expensive. Anyone have a history with them as to their quality?