I would choose 4.88 for 35s and 6 speed for sure. Will be a good balance of power and highway rpm and great offroad as well with the low 1st gear on that transmission. 3000 @ 75 on the highway: perfect. If you're going to go to 33's, try to decide on that now. I'd go with 4.56 if going to 33's, although 4.56 and 35's would not be terrible, it's about the same as the 5 speed on 4.88 with 35's. I'd try to make up the tire decision now and choose the ratio accordingly. Or worst case, enjoy the lower gearing and drive 5 mph slower on the highway.
Sorry to hear about the loss of your son, hopefully his Jeep makes the loss a little bit less hard. I'm sure he'd want you to have it.
Thank you. It does help me to cope working on it. Thanks for the information.