You very likely will. Have you reviewed the wheel directory, meaty tire thread, and aggressive wheel thread to see what would be necessary to fit them in as far as lowering and camber goes?
Wheel Directory
Meaty Tire Thread
Aggressive Wheel Thread
Here is a set of 18x9.5 +38 (+43 offset and 5mm spacer = +38) so you can see how it would fit.
http://www.ft86club.com/forums/showthread.php?t=10406
Also, 5-10mm spacers will require new wheel lugs and slip-on spacers, so look into what's required to replace the rear lugs. There are DIY threads around here on it.