Right on, 4L ! Selec-Trac all the way! That's more like the 1990's GMT-400 select between 2wd, neutral, 4hi and 4lo. That's what you want. The other one is sort of an all-wheel-drive all the time option, most often coupled with the 4.7 liter 8 cyl, but not always.
Interestingly, the '98 is the...