Just check my engines around the shop. Doesnt seem to matter wether aluminum or iron. It more of gen 3 or gen 4 ls engine. Gen 3 has the boss but not drilled. I have check my gen 3 4.8l iton 5.3l iron and 5.7l aluminum have non drilled. My gen 4s, 6.0 alu, and 6.2 alu have drilled and tapped bosses
