Looks like I'll be busy for a little while longer. My original plan was to only replace the lowest part of the trunk floor the full width. Only way to get full width that I could find was to buy complete pan with braces. The more I look at it and knowing the work, wire and gas involved I have decided to replace the whole thing, braces and all. I did see where it was recommended to get a 69 chevelle pan because the upper rear section is a closer dimension /angle to the Buick, this is a 71-72 AMD from the parts place. The ribs are correct but the spare tire loop is not (maybe a flint versus gmad thing?)and no bracket for the jack . That may be correct but the ribbing looked completely different and I don't need the upper tail section. My plan is to leave the rear brace in and split the pan at the upper lip of the rear brace and butt weld new and old there. Then I'll only have to finish/grind weld on the inside as the outside of the seam will be covered by the brace/rear body mount lip. Also by installing the whole pan I will only have a gagillion ( tech term) spot welds to do around the perimeter and not a butt weld all around the have to finish inside and out.