Reading those threads, I have to bring something up:

An 04 L26 I recently picked up from an Impala had the standard metal pan with standard windage tray gasket.
The 04 Impala had the L36/L26 hybrid engine. It was technically a L36 with a L26 block, crank, pistons, rods, valve train, and heads. The UIM, TB, LIM, fuel rail, electronics, oil pan, water pump, etc would be identical to the L36s.

I may know a thing or to about that specific year L36.