How old are your Kenmores? Some in the 80s were made by New Home (Janome bought them) so a foot for a New Home should work. Does either of the machines have a 2 position foot lift? Pfaff did on older machines.
Leah Day does have a a tutorial for a floating foot.
Here's a link to some sewing feet for Kenmore. If none of these, generic high or low shank whichever you have should work.
http://www.sewingpartsonline.com/ken...sser-feet.aspx