Is it the old boxy style or the newer (88-up chevy 1500 style)? If it is,
you might look into switching the door panels from a later truck. From like
95-on they had spots for a 6.5" and a tweeter. Most likely you would need to
change the door panel and the metal plate behind it. On the inside of the
bare door the main panel bolts to the door shell, so it should be fairly
easy to change....

Or you could build kicks.

Jay