Tripped over a comment on a Challenger forum that some people get over-rev codes with a 3.90 rear gear and an A8 because it can't shift fast enough in the lower gears. Just an FYI, doesn't mean everyone that does that has an issue, but sounds like some do.
The Challenger 245/45R20 is about 28.7" tall so you would be shorter with either tire. So your 2.76 would be like running a 2.83 or 2.97 in a Challenger, depending on which tire.
BTW, the 845RE (A8) V6 Challengers got a 2.62 with the performance option being a 3.08. R/T's and Scat Packs Challengers got a 3.08 or 3.09 depending on if the axle was open or had a limited slip. Hellcat's only come with a 2.62 rear gear, no 3.0x option.
