78 k15 Transmission swap
 

I have a 1978 K15 4x4 that I'm replacing the clutch in. Right before I drove it onto the ramps (a hard task with no clutch) the truck started making a nasty grinding noise in or out of gear. My bro thinks it might be the throw out bearing but anyways I would like to replace the whole transmission with a 5 speed. Is this possible and if so how hard would it be?