you should be able to swap the engines. The differences are:
1. in 1998 they changed the pistons to a deeper dish
2. Camshaft changed in 2000 model year. Slightly more lift. The 2000-later cams are considered the better cams. Note the hp jumped up for those later years from 230 to 245 and 250. and torque from 335 to 345.
3. Pretty sure the injectors went to the red corporate 23.3 lb/hr injectors in 2000 as well. That would be the only part to affect you