Heres a picture of how your original setup should look like(dont mind the drivline angle thats air bags deflated and ive since corrected the extreme angle) just look at the center carrier bearing:
Ive also have read that the type with the bottom mounted carrier bearing like you have installed is a bigger driveline(1.3780",1.5748") then the style that hangs from the top(1.1811"), so if you were to switch to the right one for your year truck you would have to swap in a whole driveline and not just the different style bearing!
I agree with captain fab on that the bearings that hang from the top are crap, ive had three come apart(just pinch welded together) and finally had a buddy put a nice thick weld around the last one to make it work, they do sell a billet one that cost $100 but ive never used it, I would just keep the setup you have since it is a larger size drivline and a all around better bearing setup and would just have it remade longer.
you should be measuring with all the weight of the truck resting on the wheels, so if you can crawl under the truck and measure with out jacking the truck up that would be ideal, but if you have to jack the truck up make sure you have the jack stands placed under the axle and not on the frame allowing the axle to hang.
I believe you should only need to have the first piece of drive shaft coming off the trans remade not the whole thing, but i would double, triple check everything!
heres a link to measuring a two piece driveshaft:
http://www.actionmachineinc.com/mult...haftguide.aspx
and you might be able to bring the center carrier bearing down a bit if you remade the bracket its bolted to shorter, but you can probable get away with were its at now...and your cross member looks just like mine so i dont think its bent...