Moderate static on 255/70/15's

[DoobieBrother]

Starting a low budget build with my son on our `68 longbed. It has 255/70/15's on 15x8's on all four corners. Looking to figure out what is the simplest bit of moderate lowering we can do to better tighten up in the wheel wells while keeping the current tires/wheels and getting no rubbing and retain a good ride quality. I'm thinking like a 2/4 but unsure.

Would appreciate what you guys know about this combo and if you have any pics of trucks done this way, would appreciate it.

Thanks!