305's are a little uncomfortable on the classic body style 88-98 pickups, without at least a body lift. It has been proven though, with the right wheels and backspacing, they will barely rub... if they do it will be minimally. However, if you really care about your investment, and you want to actually wheel on these tires consider a small lift - perhaps a 2' body lift - to make everything work properly together.
The new body style pickups with the big front bumper, actually fit 305's on the stock wheels with no trimming.