If you do a search, you'll find a ton (literally) of threads about this topic. The first option is whether or not to cut the dash. If yours had been cut in the past, to install a DIN-sized receiver, then the question is moot. If it hasn't, then the question is what kind of radio you want. If you don't want to cut, then your choices of 2-shaft radios is limited as far as the aftermarket is concerned. Oh, there are some nice ones, but if you're a techie-sort, you may not be happy with the old school look. If you're wanting to install one with a DVD player and an LCD display, then cutting it is your only option. There's a member named Mahanian, who has a billet aluminum part that dresses up a cut dash and allows for the clean install of a single-DIN receiver.
As far as speakers are concerned, you have options. One of them is a part that attaches to the kick panel and houses the speakers. Look at
www.lmctruck.com for their catalog. That will show you what is available, not only from them but from vendors on-site. The other option is making a hole in the lower part of your doors, like mine has had in it for years. No, I didn't do it, but it's what I have. The problem with that is rain. You need to make the speakers water-proof, or they won't live. I think that there are housings that are available to fit the backside of the speakers. I don't have a link, but I need to look.