1. Does the distributor plunger/piston on a 1.6L NA I.P. have to be replaced as a pair with the distributor head or can it be replaced seperately.
2. Does anyone out there have a spare one that they are willing to part with

....preferrably in the GTA, but anywhere else will do.
Thanks
They are DEFINITELY a matched set - you can't replace one without the other.
OK then...next question
Are the distributor heads/plunger interchangable between say a 1984 IP and a 92 IP, both being NA or would a turbo IP distributor be any different?
my fuel pump is made from a 1.5 yellow dot casing, mostly turbo internals, a 1.6 n/a pump head, and some internal mods. a pump head is a pump head, the injection pump doesnt care.
... unless it's a 12mm pump,
the plunger won't mwork with the cam plate,.. without machining.
It's not limited to 12mm pumps where the plunger won't fit in the cam plate.
You won't run into that problem with 84/92 pumps though.