either 1 of 2 things here in michigan, you will need to get the title to the cab, the title to the frame/rest of the truck, have the state police inspect it & sign off on it, it then becomes a rebuild w/ 2005 model year...........
or do what I did, pull the windshield, remove dash pad, remove a big chunck of the new cab around the vin, cut the old dash to match, weld it up & when the dash pad is on, nobody will even see it