I'm about the same size as you. For a start you want a lowered floor, which is common, if not standard, on newer cars. Unfortunately you budget points more towards a few years old, however lowered floors can be retro fitted.
Type of seat makes a big difference too. The more modern sport turbo seat gives more room than the traditional seat. Shell type seats probably give more room yet, but I've no experience of them. I'm sure removing runners can add a bit too.
Finally, I spaced my steering column down at the front and up at the rear for more room. This can easily be done but will mean altering the hole in the dash.
Really finally, I found changing to a smaller steering wheel and moving it about 5 inches closer to me made a huge difference to comfort and control.
The bad news is most of these changes require a bit of cash as well as time. How much is variable though.