Just a couple of points to consider.
Spare parts are getting thin on the ground and very expensive.
A standard WR is 200 hp[148kw]it takes a lot to get significant power increase.
UR quattros are heavy beasts and they don't chip like the later cars.
You would always be able to get another shell for the A4 if the worst did happen.
Neither car fits into a historic catagory if that is what you intended.
$5k pounds quickly becomes $25k A Dollars when importing.
Purchase price+shipping+insurance+Aussie sales tax+GST on the lot.
And I forgot you need an import licence in advance.At least you can get it registered without modification,at least in QLD.
I looked at this option and then went local,try this link,there was a Melbourne car that could suit you if it's not sold.[prepared for targa Tas but didn't run]http://www.qsz.com.au/
Simon offered me a couple of cars the one above among them.
Be very careful bad ones cost a fortune to fix.
Go here as well be fore you buy
http://www.isham-research.com/quattro/
Good luck :kiss_rings: