You've come to the right place for advise. There is a lot of knowledge on this forum. First of all, where do you live? That will help everyone to give you advise on car prices. If you have any in mind, list them and I am sure we can help out.
I have had a lot of muscle cars over the years, but went for about 15 years without one. Over the last few years, I was getting the fever so bad that I couldn't drive down the road without looking in back yards and fields for some old car that I could afford to pick up.
5hundo is right on the money. I live in San Diego. I found tons of cars back east that had killer prices, but I didn't have the money to go look and then get the car back to the west coast. I missed out on a couple cars here and there, but it worked out for the best because I finally found my dream car last October.
My advise is to be patient. GTO's, GS's, SS's, etc are always going to cost you more than a lower line like a Lemans, Skylark, Malibu, etc. If you hold out and keep looking, you will find the right one. You might even just start paying more attention as you drive around. If you see something, stop and inquire about it.