I used the hidden type stereo as well but my speakers are in the original location behind the dash grill (www.ClassicParts.com Item #69-831) Stereo/speakers work great and you can plug any modern device known into it. The small readout/control head I mounted between my sunvisors. I also went with a hidden antennae that was installed with adhesive to my bed wood (sunny days only truck).
http://good-times.webshots.com/photo/2731952780102454676kbLHxp
http://good-times.webshots.com/photo/2281794570102454676JapLms