Originally Posted by new
Actually I did load the original book into all of my 3 kindles. Before entering into Calibre. I just do that after for safe keeping.
Convert the HTMLZ version to "old" MOBI in Calibre and see if it is more readable on your Kindles (check it first using Calibre's viewer). This should give you a standard font, but if the OCR was not effective there may be many typos. If there are many OCR errors you can either give up or go pdurrant's HTMLZ -> ePub+Sigil -> MOBI route.