Air shock options

If you take a look at my profile pic, those are N50-15's on 15x10 rims. Needed air shocks to clear those but it had a B body rear end in it. Will be stock width now. I want to get some wide rubber under it again but not at the risk of throwing the speedo off too much. Thanks for all the good input. I will look into all options.
Rumble mentioned earlier. Do it once and do it right! Buy Quality Automotive Leaf Springs, Coil Springs and Suspension Parts for your Classic or Antique Auto