Dana 40,,,? it's either a Dana 30, or Dana 44.
IMO if it's a Dana 30 it's not an upgrade from a stock Dana 35 TTB arrangement. then again, you said it's two wheel drive so i guess any front-drive axle is an upgrade, right?
keep in mind with explorers a major drawback to an SAS'd front end is you will give up a lot of upward wheel travel since there isn't a whole lot of room under the engine in the center for the axle to move into, so expect to do at least 6 inches of lift or you'll be on top of you're bump stops constantly.
you'll need to change the tail housing of the transmission as well as the tail shaft in order to make it fit onto a transfer case. i believe the transmission needs to be disassembled in order to do this so it might be a good idea to just find a junk yard transmission (or buy one from a trans shop or something) which is already set up for 4x4, maybe you can get the transfer case with it.
if you have an electric shift transfer case, you'll have to work out something to run the shift motor as well. another consideration would be a divorced transfer case, which would work with you're existing 2 wheel drive transmission. you're rear driveline would be rather short and you might want to have a custom driveline built with a double cardan (SP?) instead of U joints for the angle if you're going to run much lift... an old divorced t-case would also solve you're problem of t-case shift electronics (although you would have to cut a hole in you're floor pan for the shift lever to come through)
anyhow, i'm in the middle of a dana 60 SAS into my explorer at the moment, so you might want to fallow the thread and pick up a few things.
here's my thread
http://www.explorerforum.com/forums/showthread.php?p=2558300#post2558300
if i were you i'd probably sell you're explorer and buy another one which is already 4x4. it would save a lot of head ache, and probably end up costing you less ultimately.
i honestly don't think 3 weeks is enough time to collect all the parts, and do the whole project unless you have a lot of experience with fabrication, and good parts access. mine has sure turned out to be more work (and money) than originally anticipated.
