Uh, wow. Yes, that's the bleeder screw. It's not a "non-standard" part; it's the original design for the upper radiator hose.

That design was replaced part way through the DII production run. It had by then become known as a failure point, where the screw and its mount would "blow out," causing a catastrophic failure of the cooling system. In the updated design, the bleed screw was moved to the T fitting. I recommend you spend the few bucks to update the upper radiator hose in your truck to the "new" design version.

I know this in part because it happened with my truck. After I replaced the headgaskets 11 years ago this month, the cooling system was again pressurized and two weak points were soon "revealed."

First was the bleed screw. It blew out mid-way through my 15-mile drive home after work. Thankfully I was at a stoplight next to a gas station. I pulled into the gas station lot and used a golf tee held in place with some duct tape to plug the hole well enough to limp the rest of the way home after topping up the system with water. Fun times!!! The second weak spot revealed was the throttle body heater gasket; a well-known problem.

 

Yes, that's funny, you still have the factory bleed screw which was in the upper radiator hose. Never see those any more!

They then replaced it with one in the T that we're all familiar with.

 

Just convert to the inline thermostat mod and you can forget about bleeding, bleed screws, plastic tees and plastic thermostats. In your case you probably should change that top radiator hose as it is at least 17 years old

 

rear side you mean the side facing to the passenger compartment?

 

same with mine