I was given a set of Nitto Grapplers 315/65/16s. Still a lot of life left on the tires. Was wanting to put them on my Ranger but the fit looks like it will be snug. Especially on the front. Looking for advice on whether they will fit or not. Currently running 255/70/16.

 

They will not only be snug, they will rub badly or not fit at all. You stated 75 profile in the title and 65 in your post. I ran 11.5 x 32 - 15 tires on my 02 Ranger with a 1.5" torsion bar lift, and they would occasionally rub. the 315 x 65 -15 tires would basically be 12.5 x 32 -16 and would have serious rub. You may be able to install them and drive straight but turning would be a problem.