The 8/8 plane would likely be intended for joining 1-in stock with tongue and groove. These planes are usually set up so that roughly 1/3rd of the intended width is the tongue, with approximately 1/3rd remaining on each side. So, a 8/8 plane will probably have a 3/8" iron set to make the groove between 5/16-in and 3/8-in in from the edge. I find the 1/4-in wide, 1/4-in in planes to be the most useful.