Well... you have to cut the floor anyway for the automatic. Just cut the 4-speed hump out carefully as owners will pay good money for that piece! BTW, for what is worth, you may want to consider a Gear vendors overdrive or a Passon 5-speed. I've already done most of the research on this and if your vehicle is already set up for manual transmission, its a lot less work, time and money . Unless of course you are stuck on switching from manual to automatic.
Love to see thread on this if you decide to go this route. Good luck with it!!