So just springs moved in, you didn't widen the tubs?
Personal experience in 2 69's. offset kit allows 10.50" and that is pushing the limits. The leaf spring is the first thing you'll hit. The inboard kit with tubs 12.50" (might have been able to squeak a touch more under it)
If you run a taller rim yielding less profile to the tire/rim combo you can go a bit tighter as air pressure and sidewall deflection aren't as pronounced.