Before you go off the deep end IT DOESN"T SOUND THAT BAD. I've heard plenty of LS1 cars that sounded exactly the same that run forever.

Before you try any lucas or other heavy oils I think I know what your problem maybe. I want you to go get a few qts of Pennzoil high mileage 10-40 oil. Drain a few qts out and put the pennzoil high mileage in. It will swell the seals and oring at the oil pump and my solve your trouble. Will take a few 100 miles to help, I would let it idle for a 1/2 hr or so after you put the oil in to get it mixed well and soaked into the seals.

Sounds EXACTLY like many other LS1 engines I;ve heard when the oring leaks air into the oil, the lifters will knock and tick and tap. You may also notice the noise is loudest towards the frt of the engine.

I've owned 2 LS1 cars that had this problem from the factory. The oring shrinks over time and starts to let small amounts of air into the oil.