too much tire?305/50-20
 

i have the front fender well at 28.5" and the rear at 30.5" high on my 85 gmc.
will a 20" wheel with a 305/50/20 be too tall of a tire- will it be way too much up in the fenderwell and rub all the time?
truck has 3" spinfles in front and shackles out back.