You mentioned your friend's is a Rubicon, that came with 4.10s if it's a manual. 3.73 if Auto. My new JKUR w/ Auto has 410s. ordered as an option.
I'm and old guy , too, just looking for a capable vehicle. I'm going to pretty much duplicate my LJ by going with a 2.5" Teraflex Long Arm, Adj Track Bars F&R, Exhaust Spacer, possibly the AEV Geometry Correction Brakets. For wheels I'm going with AEV Pintler, the back spacing is correct for 35" tires without spacers. There are so many opinions on tires that you'll surely get confused. I'm a Hankook dealer and will run their LT315/70R-17 Mud Terrains.
Win