I took the original chassis and split it into three parts:

1. Rear section 2) Mid section 3) Front section

I added midline body mounts to the front and rear sections and opened the pod location slightly. I also added holes for front axle adjustability.

You will need to open the files in a CAD program (I just use Tinkercad) and set the wheelbase by lengthening or shortening the mid section. Then combine all three sections prior to printing, and you should have a chassis perfect for wider cars.

Edited to provide the files for each section.