Hey James, probably a wise decision re the GTA and drug dealer caper, however, and as per my previous advice seriously mate, now is the time to pounce. There are a lot of cars out there not moving for various reasons, and I would suspect owners willing to haggle. But be aware, given the budget you are talking about you are not going to find the perfect car, as these go for much higher prices, but you should be able to find one you can enjoy and perhaps do some further tidying up on.
In thinking about what you say you want, I just did a quick check on carsales and there are at least 3 2L GTVs that fit the bill you are talking of, especially in terms of both condition and asking price.
There is a '73 silver car for $11.5K in NSW. On steel wheels with very tidy exterior (paint and panel straightness), very tidy interior and engine bay. According to the seller, the car has its service records (that is good), with recent work done to the brakes and a couple of other matters. Comes with new Pirellis, garaged and never driven in the rain. Supposedly has 239,000km on the clock.
The next one is a '74 Le Mans blue one with tan interior, on Momo vegas (read both relatively rare and expensive wheels), with a tidy interior and exterior. The engine bay looked a little scruffy but supposedly very good mechanicals. Supposedly has 49, 748km on the clock but I would expect it has been around once or twice. It is in Victoria.
The third one in your price range is a '72 Navy Blue one for $14K ono, I think in NSW. The engine bay looks tidy, carbs have ram tubes and socks (so read induction noise), it is on alloy wheels, apparently good mechanically and has had some minor rust repairs done. If it were me, I would want to check that properly to make sure it had been done correctly. Replaced headlights with high power units. The bumpers are removed but come with the car. Supposedly with 90,000 on the clock but I again undoubtedly at least once around the clock.
There were a couple of other cars available for between high $15-16 + but one was auto and the other to my mind looked like a tart box.
My point is they are out there. If your budget were to stretch higher to around the $20k mark I am sure there would be some really superb cars.
My pick of the 3 listed, if it were me, is probably either the silver or Le Mans blue one. As ever though best to do your homework and/or get the car you are interested in checked out by an Alfa (preferably 105) specialist.