Graeme, we keep an up-to-date list of Cobra manufacturers on our site.
http://www.snakebite.com.au/kit_man.html
I would have a good look at this forum as there has been a lot of discussion about the different kit types. Try using the search function.
A good starting point would be to roll up the a NSW club meeting and see the different kit types in person and talk to their owners.
To determine whether you should go new or 2nd hand and also which kit type would suit you best, you should think about what you specifically want out of a Cobra...The following questions should help guide you.
1. Do you have specific requirements for your Cobra(look, design, space, performance etc)? If so, new might be the best option. If you are willing to compromise(a lot) then 2nd hand could satisfy.
2. Do you want an original style drivetrain? e.g. Ford 302w, Ford 351w, Ford 429/460 etc. If so, then 2nd hand is your only option and these engines can no longer be complied.
3. Do you have specific requirements on what suspension setup your Cobra should have? e.g. Jag, modern independent, fabricated or combination of.
4. Are you concerned with how original the body shape is?
5. Do you want(or care) if your Cobra has a separate body/chassis unit or monocoque body/chassis unit?
6. Do you want to deal with a local manufacuter or are you happy to deal with someone interstate?
7. What sort of timeframe are looking at? To get a professional to build a Cobra & get it complied will take around 12 months. To build one yourself ranges on average from 12 months - 5 years.
8. Do you have enough funds to purchase a Cobra upfront or would you prefer to pay for it over time?
9. What do you want out of your Cobra, what do you want to do with it? Weekend cruiser, daily driver, show car or motorsport.
10. Do you want an original looking car or as close to original as can be made? Then 2nd hand is the best option, especially buying a Cobra that is already registered and can be rebuilt close to original specs.
11. Do you want a carby engine? If so, then 2nd hand is the best option.
12. What is your budget? 2nd hands cars of any substance start close to $20k these days. $50+ starts getting you into the better 2nd hand cars. You would be looking at around $60k+ to build your own car. Professionally built Cobras would start at around $70K - $80K.
Hope this helps. Owning a Cobra is definitely one of the best lifestyle choices I have made. Good luck with your search.
(I'll write this up better and put it up online, let me know if there is anything I have missed)