What Avon said ^^^^^
The 1975 2 door is the most desirable and will therefor fetch the most coin. (preADR27a the only MK2 you can legally run webers on)
What will it go for?
Depends on how many others are on the market at the time, who is buying, and how long they have been looking for.....
You have the 3 big ones in your favour, 2 door, little rust and year.
Shaun