What kind of ABS does this truck have?

The first thing will be to get it scanned with a tool that can read the ABS codes. It could be a bad speed sensor or a short or a bad module but without scanning it to find the code first anything else would be a guess. Unfortunately, most of the places that do free scans won't do anything except engine related codes so unless you have a scan tool that can read the ABS system it's likely going to need to go to a shop.
As for which system it has, they offered 2, one was a rear wheel only system that used a load valve in the rear and won't trigger a light unless you broke a brake line and lost all of the fluid. The other system was a 4-wheel ABS system that uses an EBCM that mounts in the left side of the engine compartment, easy to tell if you have it because it uses a large module with brake lines coming out of it. If the fault is in the EBCM itself you will need to replace it and have it programmed to match the vehicle's options like tire size, engine size and such using a dealer level scan tool.

The ABS uses parts on the truck that don't change. Tires won't alter it unless you go to a very different size. I would start with the scan. Wouldn't be good to replace and program a multiple hundred dollar module because of a 10 dollar connector.

That truck would be handy in Florida. With those tires I would check that the ABS is still there, it may have been disabled and now the light is always on.

That module would be up under the hood if it has the all wheel ABS. Pop the hood and take a few picture of the left side of the engine bay and we can tell you for sure.

Hi,

I noticed you haven't been contacted in a couple of days. Have you been able to make any progress? I'm interested in knowing.

Take care,

Joe

Hi,

No problem whatsoever. Let me know if there is anything I can do to help.

Take care,

Joe

Hi,

I attached a pic below showing the front wheel speed sensor location. Confirm they are there. If they are, do you know if the scan tool can provide live data? If it can, check to see if the wheel speeds are the same while the vehicle is moving.

Let me know.

Joe

If the light is on it should have codes stored unless the scan tool you used cannot talk to that module, not uncommon with some tools. As the light is on and you have the 4-wheel system, check that all four fuses are good. Use a test light to verify power on both sides of the fuses. Then if your tool can read live data look at the three speed sensors as Joe mentioned. Being it's a lifted truck it's likely that someone disabled the system by pulling a fuse or didn't connect the sensors. Also, common because the harnesses need to be extended.

It can. The system uses multiple power sources. The 50-amp powers the module itself. Remove it and the light comes on because the PCM no longer sees the ABS module. The other fuses power different parts of the system and a fault in any of them will turn the light on. However, the 50 amp is one that, if it is removed you wouldn't be able to connect to the module. So, we start at the powers and grounds.

No rush, I know what it's like when you need "roundtoit's"