You have a couple of options short of ripping out everything
. I think which you choose depends on what you want the quilt for. If it's intended as an heirloom or showpiece, I'd explore #1 below. If it's for color, beauty, and keeping you warm, #2 or #3.
1. See how far off you are between the older and the newer. If just a smidge, you could, take out and adjust one or two seams only on the short (or long) strips to make them almost-match.
2. Snip the ends of the long strips or add a little piece to the ends of the short ones.
3. Add a little piece in the middle (or at some random point) to the short ones.
For #2 or #3, you wouldn't worry about matching seams all the way across. Scrappy quilts are allowed to be scrappy and not match!