Shifting Lever Unit replacement/interchangeability on Shimano 8 speed XT/XTR shifters

Are the levers/internals interchangeable? Meaning will they all fit the same housing or can I swap one for the other if needed? Will any 8s XT/XTR shimano 8 speed shifter lever fit any other 8s XT/XTR housing?

Looking at the repair manuals, the part numbers are very similar, and the bolt patterns and housings look very similar.
XTR
([Sl-M950][4], SL-M951) [6BT 9801]
XT
(SL-M739, SL-M740) [6BA 9801]

(Everything that comes after that seems to be a sealed entity, or made differently)

pdf
[4]:
https://si.shimano.com/api/publish/storage/pdf/en/ev/SL-M950/EV-SL-M950-1629.pdf