Just doing a short search on RJ I was seeing nice Mustangs in the $5000 range running. Watch Craigslist also. I am not a Ford guy but I would race one of them in a heartbeat. Plentiful cheap parts to make a nice footbrake car to get started in. The G-body chevy cars are the same way. I have about $13,000 total in my roadster but I was really patient and bought parts for a long time so you can go fast on a budget. Good luck with whatever you choose and I hope you get on the track soon. We can never have enough new racers.
Curtis