Will a truck cap that fits the crrent 2011-2014 Super duty, fit some prior years also?

 

2008 to 2014 should be the same. 1999 to 2007 should be the same. So to answer your question, a cap for a 2011 to 2014 should also fit a 2008 to 2010. Depending on the manufacturer, you should confirm with them - that's the only real way to know.