To really be of much help you'll need to provide the details of your setup. Gearing, tires, if OEM stock Carter BBD (computer still in loop).
FWIW, I had trouble with my OEM computerized carter going much above 3200 rpm or so until I did the Team Rush upgrade. After the upgrade I could go to 4000 rpm if I wanted to. But seeing as the 4.2L makes peak torque around 2000 rpm, and peak horsepower around 3200 rpm, going above 3200 rpm isn't really going to be of any benefit.
However, bogging in 5th gear could be due to tall tires and tall gears. Pair 31" tires with 3.07 gears and you aren't going to get much power out of 5th gear.
If you still have the OEM computerized carter BBD check here: Adventures Under the Hood