Thanx so much for the advice so far. Here is a quick update.
Today I began the process of pulling the rear axle apart. My plan was to get it apart, take a look at the axle shafts and third, see where the problem was and go from there. Problem is I only had part of the day to do so, and I was having a HELL of a time getting the drums off, so after pounding on them for an hour, I decided I have to put it back togethor and wait for another day. (I have to work). I did drain the fluid and there was a real nice shimmery hue to the oil and metal shavings on the magnetic plug....so thats great. I re-attached the rear driveshaft with the rear tires in the air to see if i could get a pattern out of the clunking, and there is a definite pattern ...something like clunk clunk....clunk.........clunk clunk...clunk. So anyways I pulled the rear DS again and will limp around in FWD for the next few days (I figure the damage is already done in the rear, can it really get much worse?) and hopefully one day next week I can get a day off and put the 4.10 third I have as a spare in.
I heard somewhere, and maybe I am wrong, that the front and rear thirds are interchangeable? If this is the case would it be better to have the 4.88 in the rear or the 4.10 in the rear? Ideally im going to find another 4.88, but for short term I just need to get the thing driving normally in 2WD as soon as possible.