Only in a 1500 back then. That's just what I've found. 99-02 2500LD was 5.3/6.0 4L80E only.
I get stuff wrong all the time, so who knows.
the 99-00 2500 light duty could only be had with the 6.0 and 5-speed or 4L80.
no worries, its soooo easy to get them mixed up/so confusing the way GM set things up, there are many oddball combos out there...
ben