Your 98 is stock from what I can see in your sig, I think you will like the new trucks. I kept my 98 for a toy, but drive the 04. 5 all the time for work. It is a nice enough truck, but that is all it is to me. Ride is good, brakes are AWESOME, handles corners like a truck. Never really had a "handling" problem with the 98. Maybe I don't expect to much from it in the handling department but never had any complaints. Power is decent in the 04. 5. I have about 1,000 lbs of tools in the back since new and for what I use it for it has more than enough power.
98 12v = 254,000 km's without one single engine problem. Nothing.....
04. 5 24v = 20,880 km's trouble free miles on whole truck. Very happy with both.