You can do two different doors or two different ignitions, since there's only one set of pins for each cylinder.
You
can't do door and ignition keys on the same blank because until OBS trucks, the oval (door) and ignition (square) keys had opposite keyways.
--_. or _--.
Or you can do as I did and get a later set of door cylinders keyed to your ignition key.
Always best to have the locksmith read the cut from the VIN, or use the unused aluminium key that came with the owner card in the glove box.
Jim,
Lil'Red is a '87 F250 HD, 4.10's, 1356 4x4, Zf-5, 3G, PMGR, Saginaw PS, desmogged with a Holley 80508 and Performer intake.
Too much other stuff to mention.