A little RPM help please

[JoulesWinfield]

Hey guys, I just got my 31's on and Im lookin at new gears and speedo recalibration.
Im currently debating between 373 and 410.
Could one of you nice fellows help me out with your stock engine RPMs are at a couple of different speeds? I cant put my old tires back on cause I was running 235/75's instead of the 235/70's that were supposed to be on there.

Im looking for 60mph, 65mph and 70mph in fourth gear (OD) and a 342 rear end.
FYI - the RPO code for the 342 is:GU6.

Thanks in advance for your help,
Joules

PS. I have updated pics for yall, I just havent gotten them uploaded to photo bucket yet.

[JoulesWinfield]

Heres the before pics. I had a 2" Rough country and 235/75's for the past 6 or so years.



And the after. Added a PA 2" body lift and a minor 2" trim at the back of the front wheel wells. Went from 235/75/15 on 15x7 wheels with 6" back space to 31x10.5/15 on 15/8 wheels with 3.75" back space.


I still need some "clean" pics. But I like it dirty