ok for clarrification:
yes you have a vacuum disconnect in your front axle. What that means is that the passenger side axle has 2 shafts inside. when you shift your transfer case into 4wd a shift fork (actuated by the vacuum motor) slides a color connecting the 2 shafts together making 1.
To eliminate this:
you could buy a posi lock. This makes the shift fork cable actuated with a lever inside the truck. this still leave you with a 2 piece axle on the passanger side and a relatively small u-joint.
your other option is:
to buy a block off kit from Randys Ring and Pinion and TJ front shafts. Using TJ front shafts gives you a 1 piece passenger side shaft. This also gives you a bigger u-joint than came in your YJ. This also allows you to upgrade down the road to TJ alloy shafts. This is the better method.
the posi-lock is $200, you could probalby install this yourself if you know the difference between a wrench and a screwdriver.
the block off kit is probably around 50$, plus what the TJ shafts cost. You could get a used set for less than 100$. However this is something you probably could not do with the help of someone who knows there way around a front axle, or you will have to pay someone. This is because it comes with a new inner seal that did not exist in the axle before and they are a pain to get in. If you go this route, and I do recommend it (remember better 1 piece shafts, and bigger u-joints), I recommend Hollyoak4x4, as Brian has done alot of work for people on this board and knows his stuff. He is mopartech here or http://www.hollyoak4x4.com
I hope that cleared some things up for you.