Those items are in the MMPDS 12 or 13, I dont currently have access to be able to upload those...but an engine case is structural, so are engine mounts, which can be welded in some instances. Hell the grumman Cheetah is glued together, the skins are glued on the structural members...didn't last long but the OEM did it.

1941 Taylorcraft
1968 Charger
1994 Wrangler
1998 Wrangler
2008 Kia Rio
2017 Jetta

I didn't do 4 years and 9 months of Graduate School to be called Mister!