Hi Johnny The chassis is made from thin-walled tube and thin-walled sheet metal with a few regions of solid material.
Meshing with solid tetrahedral elements is not recommended.
Use the midsurface tool in SolidWorks or SpaceClaim to create a surface model of the chassis. That will allow a shell mesh to be created.
Some surfaces that end at the outside of the main tube will end up with a t/2 gap. Those surfaces should be extended to reach the main tube.
Surfaces that overlap with the main tube can have bonded contact to connect one surface to another.
The few solid regions can be split off and tet meshed. Surfaces should overlap the solid to connect the solid and the shell mesh using bonded contact.