I am not an expert but I can tell you the type of welder you choose to use should be based on the material you are welding.  

I was introduced to TIG as a means of welding aluminum.  

From my experience, you will acheive better results sooner using a wire feed type welder (MIG (gas) or Flux cored arc welding (gasless) )

Keep in mind CARS regulations suggest that welds should be neat in appearence...

Although I've taken a college course on the subjet and have a few years of pretty consistent welding experience under my belt, I still would not trust my life on my welds - when it comes to the cage at least.  Personally that's something I would leave to the experts.  Seam welding the body on the on the other hand...  I would consider it.

Also consider what almost everyone who's built a car will tell you - it's much cheaper to buy a built car which already has a logbook.  Not only is it cheaper you won't have to worry about whether the car you are sinking all your hard earned cash in will pass it's initial inspection and be granted a logbook.

Anyway - those are my amateur thoughts on the subject - not meant to be discouraging in any way.

Lastly, what I should done, purchase the CARS rule book before you start building, or buying.  It will give you a better idea of what you're getting into.  

Others will certainly have much to add or correct, it's a beginning at least.  Anthony

thanx guys.
Ill keep my eyes open for a 91 civic rally car maby. That way i will have a parts car.