Will this work.
 

This maybe a stupid question but I am not too familiar with the whole suspension thing. Anyway... Right now I have a 2004 F-150 with a Fabtech 6 in. lift with 35s. After having it lifted for a year, I want to go bigger. I want 37s(atleast). If i put a leveling kit on and an add-a-leaf in the rear, will it work. Or can i even do that? Or if you have any other suggestions, feel free to share.

Thanks for the help!

Yeah, some members have done that. You could also add a 3 inch body lift.