Tail light harness
 

Anyone know if the taillight harness from 2001 is compatible with the connection of a 98? I bought tail lights but the tail lights only have 2 holes and I my 98 has 3 bulbs and I know the 01 has 2 bulbs so I was wondering if I got a harness from an 01 would it fit with the connection of a 98

No, not compatible, and no, 2001 rear harness will not plug in to 1998 harness
The difference is in the Cab, in the turn signal stalk, multi-function switch, not at the rear, so not just a "re-wire" job

1993 to 1999 used 3 wire system, separate turn signals in the rear, 3 bulbs, 2000 and up use 2 wire system, 2 bulbs, turn/brake are on the same wire and use the same bulb

You can use a trailer light converter, 1998 truck to 2001 tail lights would use 3 wire to 2 wire converter
Like this one:
You would use a 2000-2011 rear harness so the bulbs and holder match, and then cut the wires off at connector to splice them
The Parking lights and Reverse lights just splice together, should be the same color wires up to 2003 I think, brown for Park and Black/pink stripe for Reverse lights

The brake and left right turn, 3 wires, go into the converter and left/brake and right/brake come out, 2 wires
Brakes are Light green wire


Or you can use 1993 to 1999 tail light lenses with current wiring