~Angry Tractor~

It's a 6 speed. What kind of HP will a programmer bring? How will the 6 speed hold up to the additional HP?

Peterbilt

03/04s = 235 in Cal for all, If it's an SO it's 250 and HO is 305. Look at decal on driver's side of engine.

Pete

CTDinMT

If it's a 6-speed, it's an HO. The manual tranny SO's (like mine) had NV4500's.
Your rated power should be 305 hp, 555 ft.lbs tq. If you look on the drivers side of your engine, on the valve cover you'll see a white sticker with HP/TQ ratings among other things.