Your driveshaft slip yoke should run in the middle third of the splines. If its not, that needs to be fixed.
If you add in a slip yoke eliminator, your going to need the drive shaft modified.
Done properly, the transferase tail shaft and output shaft are changed. Then the driveshaft end is changed and a slip yoke added.
If it was my vehicle, it would get the SYE mod. if you cant afford it, the driveshaft needs to be proper.