I would split this into ten 4' wide by trailor height panels. Open the file in photoshop. Go to Image menu > Image size: Now resize the document size to 1000% with the "resample image" box UNCHECKED.
This should give you your full image at scale with 30 Ppi. Now you want to use the ruler ( Ctrl + r to show/hide) and drag your guidelines out (click and drag from the left ruler area) and place them every 48" and every 48.25". Additional note: The Tab key will quickly show/hide all of your menus, and CTRL + or - will quickly zoom in and out. This will set up all of your panels with thier 1/4" overlap. This is where I save the file. I them crop the image down to each panel ONE at a time, and save it with name and number ( 1-10 ). Each file (saved as a medium quality jpeg with Adobe RGB color profile) is then upscaled 200%, which gives a final PPI of 70, which is acceptable for wrap standards. Print and Install.
Your welcome.
-Keith