np205 output shaft

[71stroker]

I have a 1971 chevy k-10 4x4 short bed. It has a sm465 trans. with a np205 trans. case thats wore out. I bought a low mileage set of the same trans and trans. case out of a 1980 chevy 1 ton for 135 dollars. There like new. Still have factory stickers on them.
My problem is that the output shafts are way different. My old one has a short shaft with a yoke bolted on it with a u-joint right after the speedo gear housing. The new one has a long shaft with a housing bolted on after the speedo gear housing. Its at least 4 inches longer.It is also splined for a slip yoke so my driveline wont even work. I just had new drivelines made for my 4 inch lift so I dont want to have a new one made. I was told that I could just unbolt the housing and shaft and swap them out. When I unbolted the new one I realized the shaft has a helical gear and other stuff attached to it. I started to disassemble it all and realized I needed some help. I cant find a book or any detailed info on this trans. case. No one I know has any clue what to do and all the shops around here wont help me without simply paying them to do all the work. Im trying not to spend my money on labor .
My first question is I need to know if it is at all possible to even swap the gears and other stuff to my shaft before I tear any more apart. Im assuming that putting my old shaft with the old gear and bearings in would be a bad idea considering the gears would probably wear funny.
My other question is That I need to know if the gear needs to be timed with the other ones. Ive worked on semi truck transmissions and splitters and know that they have to be timed or bad stuff can happen. Im at a stand still until I can figure this out. I would like to do it on my own so I can learn about this stuff. Any information or suggestions will help at this point. I will post pics if necessary but never could get them to work before. Might need help doing that. Sorry this is so long but I wanted to give all the info I had.