Where would be the best/easiest place to connect a negative wire to a ground from the interior?

 

Where in the interior? I've used the seat bracket bolts before with good success for anything under the seats. For anything by the dash, find an existing ground point and add it to it.

 

Yeah, probably under the dash. Thx!

 

You can ground to anywhere on the frame of the car, as long as you remove the paint at the point of contact.

 

just fyi you shouldn't use the seat bolt bracket fir a ground unless you test the resistance (ohms) with a multimeter. Grounds exist all over the car, usually a great place for a ground on any vehicle is in the kick panel (driver side)
I use that area for alarms often, and I just scrape the paint away with a wire brush on my drill. But our cars are a unibody vehicle, which means most areas on the vehicle that are the frame will be a great area. Always test though, some grounds can be a descentbground for low current, but as current increases it gets worse.

 

Thx guys... I ended up just going through my firewall and using a ground under my hood close to the windshield.