Trouble staying straight on hw
 

I just picked myself a 1994 2500 2wd cummims with 115k on it. I've only driven it for about 4 days and when driving on the highway (55-65 mph) it seems to want to swerve a little bit. I'm not to familiar with older trucks and handling. The tie rods seem fine (no real play). I dont know if i should get a steering stabilizer because I've never seen one on a 2wd or if it would help my situation at all.. but if anyone could give me some feedback or advice that would be helpful!
THANKS

I would start by getting the front-end alignment checked. Directional instability can be a sign of insufficient caster. If there is anything worn/loose, the alignment guy should tell you - though you can check some of that yourself.

I had a similar problem and went for alignment. Turns out the pitman arm was loose on the steering box output shaft. I had let it go too long and the splines were worn such that I needed a new steering box and pitman arm.

check all the front end joints. trackbar especially.
Check the steering damper and consider an upgraded version with more damping power. The version that goes from the axle to the tie rod makes more sense than the one that goes from the frame to the tie rod.
If all that is good.. oversize tires will make the truck wander more. wear from failing ball joints can grab ruts and pull you around, sometimes violently if the road is rutted.
Stock steering is usually sloppy and the rate means more wheel travel to make a correction. borgeson box is one fix but it aint cheap.
play in the sector shaft can be fixed with a steering brace