in order to mate my Dana 300 to my 4wd 700R4 trans I need to swap in a 27 spline inputshaft. this is very simple but here's a how to anyway.
1st: Remove the input housing from the transfer case. 6 3/16 ths allen head bolts. then use two pry bars to pry the housing out.
2nd: Remove the snap ring holding the gear on the back..
I used some "choice" methods cause the snap ring pliers i had at home SUCK ! Also in this picture the snap ring already removed..
3rd: this gear will then slide right off.. Might need a lil tap to motivate it.
4th: remove this snap ring with a flat head screw driver.. and then tap the housing to losen it from the bearing.
5th: then press the bearing off the old shaft and onto the new one.. ( i used a hammer and the vise.. i recommend a press )

reverse the steps and reinstall the housing ! and you're done.