Steve shared this link to an article on Con-Ferr, which also had links to the McQueen archive. (I thought I had shared this archive of Steve McQueen and his CJ-5 Super Jeep at some earlier point, but it appears I hadn’t.) There are more details and pics of the build in the 1970 Con-Ferr Catalog… See pages 48-51 on this post: http://www.ewillys.com/2019/10/02/1970-con-ferr-catalog-pages-43-96/
Here’s the article from Steve: https://justacarguy.blogspot.com/2018/08/con-ferr-incorporated-in-burbank-made.html
Here’s the McQueen album: https://archiveimages.com/licensing/public-gallery.php?id=441&pageNum_rsImages=7
looks like it had three fuel tanks for a total capacity of 60 gallons!