Unsure of what car to buy in the 4-8k range?

First off, thanks for viewing my post.
Secondly, I'm currently drive a 97' Ford-F150 with 252k miles. I love my truck but she simply isn't going to last too much longer.
Lastly, I'm not sure what kind of car I want, at all. I'm interested in an RX-8 but not set on it yet. I'd like a car that I can do some work on, mainly cosmetic. Maybe add a new air intake or muffler, just small things. A smaller car would be great and one that gets above 20mpg. Any and all advice/suggestions are welcome!

The RX-8 is a pretty cool car, but before you buy one there are some things you should know about rotary engines. All the power is way up at high RPM, and there's practically nothing down low. The fuel consumption is pretty dismal for the engine size. You'll get better than 20 mpg, but only just. They burn a lot of oil, even when they're perfectly healthy, and every 20k miles or so, the engine has to essentially be torn apart to replace the seals. If you're OK with all of this, rotary engines can actually be a lot of fun.