i would say pick 2 out of your 3 requests lol

Im sure you can find a v8 s10 that runs 10's for $5k but mpg and reliability will blow.

1st gen neons (Can be very quick and boosted to around 400hp under $5k and still get 30mpg, but no "COOL" factor

Miata Tons of fun, reliable, great mpg, $$$$ to make fast and again not that "cool"

Civic, integra Very reliable, Great mpg, $$$ to make fast

Jetta/Audi A4 Some what reliable, decent mpg, Can get into the 13's with bolt ons

Older 5.0 Meh Mpg, but cheap to mod, and pretty reliable

LS1 6spd fbod great highway mpg, very reliable, very moddable (just have to find one for $5k

Lt1 should be easy to find, ok mpg, ok mods, ok reliability besides opti-spark

you have many options