I had pulled a half yard from the back for the fourth strip. I think you can start now and go pick up the extra half yard tomorrow for a border. A small border will move the quilt out of the skimpy stage. Remember your back is now 54", so you need to stay under that. You may have add a strip down the center of the back vertically. A border will cut it very close on the width.
As for as the five blocks - 1) all fabric isn't the same width and 2) you can't use the selvage. It will be very close, that's for sure.