I have a '98. 5 Sport... it, and all previous Sport models used a "painted" version of the OE (SLT) chrome grille... the same goes for the chrome portion of the bumper. The plastic portion of the bumper beneath the steel/chrome bumper is gray on SLTs, body color on Sport models.
At the beginning of the '99 model year, DC gave the Sport a face lift, replacing the grille and bumper assembly with what you see today. The '99+ Sport grille is taller than any of the other grilles and protrudes out away from the hood farther (at the top... a little less at the bottom). In addition, the newer Sport grille has more of a downward slope on the top surface as well as having a larger hexagon shape in the honeycomb pattern used in the four grille openings (which in themselves are a different size than all previous grilles).
How do I know this? I studied this grille pretty intensely before I purchased my own '99+ Sport grille for my '98. 5 Sport (WITHOUT the use of, or desire to use a '99+ Sport bumper assembly along with it). A couple of years ago I mated my new '99+ Black Sport grille to my '98. 5 Sport. Through careful cutting of the top of the bumper the taller, later style Sport grille can be allowed to close BEHIND the bumper instead of on top of it (as all current grilles/bumper assemblies do).
BTW, if this enhancement is anticipated, you will need to order the '99+ grille frame as well. No grille frame change is required to retro a '98. 5 or EARLIER Sport Grille to a NON Sport (i. e. SLT) Ram ('94 through current I believe).
To me I achieved the best of both worlds.