You could use the shoebox style card boxes, that may suit what you want to do. They are far sturdier than the regular shoe boxes you are using. You can fit a complete Topps set from those years in a row, there are two rows per box. The rows are wide enough to fit graded cards, so putting cards in sleeves in that type box would not be an issue.
Scott
Scott
50,000+ Red Sox cards and counting.