2004 International 4200 VT345

I have a 2004 International 4200 box truck with Allison auto trans.
I'm looking to replace the reverse/backup light switch. Would it be on the trans, or at the gear shifter inside the cab? Any help will be greatly appreciated!

 

Also is this the DT466 diesel engine? 1 door on this truck reads VT 365, the passenger door say vt345.

 

Here is the vin

 

Thank ya sir. Have any info about why all back up lights and alarm quit working all at once?

 

It is right up by under the key switch, has PRND321 it has an economy button under the thumb lock release. I can get a picture this afternoon. Thank you so much for the help!