There is another possible difference that hasn't been mentioned.  If the
'85 has the single throttle position switch and the '84 is wired for two
throttle position switches ... then the throttle bodies themselves have
a difference.  One has a vacuum port that the other doesn't have.
Bentley shows 2 different vacuum hose setups for digijet systems.
Follow the diagram for the one you end up with.

Mike
'85 GL Westy (2.1)
'84 GL 7 pass
'84 Westy
'84 Westy (parts)