Interesting. The 81 was the fastest 301 I believe. When you say "restore" what is your intention? Do you want to go back to 100% stock parts and setup? If not, what is your limit on modifications? For my money I'd be interested in playing with the turbo and cam a little bit to see if I could get some gains in the motor. As far as body parts are concerned, I would try to get factory parts (should be pretty widely-available). Repops on these are really a nightmare.
Last, even as this is a labor of love, I would investigate your current value and what it will be when you're done. Decide what level of "I just like this car" gap in the investment you're ok with.
Calculate what you think it will cost, part for part on the restore... Then double that figure. Its usually pretty close.