as mentioned they're the same TB whether it's L or HD. You can port it and sell it for a few bucks, or just sell it for cheap for someone else to port.
The one on your truck now looks to be an accufab. Clean the oil off and the blade should say the name. Unless the tune is off, or the idle set screw was set wrong, it shouldn't be causing any lean condition. As for amount of oil, that's normal. Doesn't take much to collect a lot of dirt, and without an oil separator for 55k miles, it adds up fast.