I recently bought an '85 K5 Silverado that will soon be undergoing a body and interior restoration. It still has the factory (RPO UN3) AM/FM/Cassette head unit the factory speakers (original stuff is great - except when it isn't, and the factory audio isn't). The body is a little rusty in the rear quarters and floor pan, and since the carpet will be removed for body panel replacement (and then replaced with new carpet after the sheet metal work is done), I thought that would be a fine time to yank all the factory audio hardware and install some new equipment. The dash pad has a big crack, so that pad will be yanked and replaced with a new pad, and that seems to be a fine time to put some new speakers up there. My question: What size is that center dash cutout, the place where the single AM radio speaker would be installed? 4x6? 4x10? Some other size? I don't intend to install a DVD/LCD head unit immediately, but will do so sometime this year, and I wanted to would put a "future center channel" speaker in that middle cutout (with its effiency and quality roughly matched to the L and R 3-1/2 speakers that I'll drop in to replace the cheesy factory units). I'd leave the speaker wiring to that future center channel hanging (so it'd be easy to hook later) until I have a video head unit with a center channel output. I'll also be running a bunch of extra power and audio/video cabling for future gadgets and upgrades that I'll surely buy from time to time. It's just easier to do it now than at various times in the future.