3 speed to four speed 4x4 trans swap questions

[nater]

i have a 1964 chevrolet k10 4x4 with 292 straite six engine and a three speed colulm shift transmistion and i want to switch it over to the four speed floor shift transmission. what kind of problems would i come into trying to do this swap? also in the 4 wheel drive model with four speeds did the shaft to the transfur case have give or spring move to it or was it just one solid strait shaft to the transfur case? thanks for the help in advance its greatly apresiated