If you are only a little bit off, I would try easing them all in to fit.
https://www.generations-quilt-patter...too-small.html
I would use the thinnest batting you can and start sewing the blocks together in rows, matching everything that you can. I am making the assumption that you are going to quilt one or two rows at a time. I would think about at least 4 rows sewn together, then doing your regular quilting on those 4 rows, being careful not to quilt into the seam allowance area. Then sew the different parts together, still matching and easing in the blocks. It will look good.
Edited to add: What is the name of the pattern? I like it.