Hey gang..
I have a '98 Ram SS/T I've own since new. I'm currently having cooling issues. After driving awhile, the temperatures get way up there, like a 230-245.... It has never run this warm. Last week I took it to my local Goodyear to have the radiator pressure flushed. The radiator's not any more than 5 years old. I'm thinking two things; the thermostat isn't opening all the way or I have a blown head gasket? How do I check to see if the head gasket is leaking into the water jackets? I bought a new thermostat, so I'll replace it this weekend....

Thermostat is one possibility Troy.....the other would be the fan clutch. See if there's any oily stuff on the face of the clutch unit.
I replaced the rad and thermostat on my 92 Cummins.....it was the fan clutch that fixed it.

I'll go ahead and replace it as well........ The clutch is the original one to the truck. It is clean, but has 207,000 miles on it.

Do not rule out the radiator. It may look and seem ok, and you even talk yourself into saying but it's only XX years old as you did. But I am telling you a buddy had it happen and just this year with only 3 years on mine it happened to me. Radiator was going bad. Swap it out and all is good. It sounds crazy I know, but its the truth. Mine after driving awhile, especially highway speeds made the gauge climb --it would never over heat, but it got warm at 230-235 with the A/C on. It would stay 210-215ish with the a/c off.

In talking to some rad shops, they all said and agree don't expect much out of these newer "cheap parts store" radiators. I personally felt cheated only getting three years out of mine--of course that is all the warranty is good for on the one I bought.