I just ran into this issue with 2013 Sahara with 3.21 gears. Wanted to upgrade to truetrac in the rear. I ordered 913A589 from Drivetrain America. Their catalogue shows it as fitting my Jeep. Learned about the bolt dia change after my JK was in the shop and torn down. (Ouch!) The TrueTrac is hardened steel. A local machine shop was unable to redrill the holes without purchasing some "special tool" (carbide bit, I think) and gave an estimate of "over $100". Drivetrain America said this was also the first time they had run into this issue. They worked hard to make good - took another unit off the shelf, had it redrilled locally and supposedly it's in the mail. They have also updated their website to reflect this info. I was also told that some aftermarket ring gears have two sets of bolt holes, so should work.
Sorry, I don't know about the front, but would be interested to see what you find out.