Barb in Louisiana

I take it that your border blocks are too long. You can add a small border next to your center of your quilt so that they will fit. If they are two inches too long, then add a 2 1/2" border strip down the length of the side, thus allowing the blocks to fit the length. You will probably have to remake any corner blocks to fit the new size, but then again, measure first, because if your block sizes are correct for your outer blocks, then your corners should fit perfectly.

Pictures please.......
Edited to add: To make sure this would work, mark a piece of fabric the amount you think you need to add and just lay it under your center. Put your blocks next to it. Does this work for all sides? Sometimes, the best thing you can do is ditch one of the blocks on the outer border and put some small fabric pieces in between your other blocks to get the border blocks where they will fit. If you don't have corner blocks, then upsize these, if needed by adding small borders on adjoining sides.
: Your border blocks only fit down the sides. Your corner blocks will go all the way to the inner, center part of your quilt. So all side borders will be the same size.