is it possible to change output shafts between various model T5 gearboxes?

I am looking to put earlier (1985ish) T5 components (extension housing, shifter components) into a 2004 model T5. As the later model boxes have an extra 3" in the extension housing which moves the shifter back 3". This is too far back for the application. From all the images I have seen it appears that once the splines end the diameter of the shaft is reduced so I am unable to simply shorten the shaft and extend the splines. My new plan is to swap the shafts over and put the gearing from the 04 T5 onto the earlier output shaft. I don't have model numbers in front of me right now.