Nobody home, leave a message at the tone
KUID numbers and where you got them, people will be kinda reluctant to help if they gotta figure out what "connys cars" might be. For the basics, the mesh has to have an a.cabfront attachment point - if it doesn't have one you'll need to add one with PEV attachment maker. If it does have one, or after you have added one, then it's a simple matter of selecting "interior" in content creator, then clicking the button for the new interior tag to select the interior you want.
If you're talking about a passenger interior, I don't know for sure - the one I played with I added an a.cabfront attachment and my "invisible" cab as an interior, so what you see is the interior that's normally visible only from the outside. See the CNW bi-level commuter car 1,<kuid:522774:100408> for how I did that.