Buddy of mine has a 66 Satellite Hemi Auto that has I think 255-60-15 on 15x8 wheels ( don't know the backspacing ) Next time I see him I'll make sure but I dont think they were 275's

Stock rear suspension and no air shocks. With 2 adults and normal driving its fine.
They will rub if he throws the car into a curve hard ( really aggressive driving) or they will rub if he puts people in the back seat and hits the slightest bump.
90% of the time its just him and his wife. He's 63 so aggressive driving sprints is extremely rare