*gets up on his Soap Box*
Preach on Brothers!
I have a '90 Astro Van with a bent 6 that gets about 350 to 400 miles per tankful with a 24 gallon tank. I kept my '94 Cav when my wife went and got a new '04 Cav last year just so I could save some money on gas. I get about the same range with my Cav as the van but with only 12 gallons in the tank! :p
Unless your dealing drugs you won't be able to afford $3 per gallon and have any crusing time this summer. Stick with the 250 and give it some bolt on power adders from Clifford or one of the other guys and live with it.
Maybe a new intake with dual carbs and water heat? Split headers will make it sound mean... Let that puppy breath! Dress it up with some crome and make the other guys go "WTF?" when you pop the hood. RapRap's '40 Chevy sounds like a Big Block at idle until he hits the "LOUD" pedal and it revs like a small block on steioids.
The first thing you have to do is make a plan, which is why you asked the question in the first place. Start with the basics:
1. How much can I afford?
2. How fast do I want to go?
3. How cool will it be?
Now ask yourself the hard questions:
1. How much can I really afford and still eat?
2. How fast do I really need to go if it's not a Bonneville Racer? (Cops love pretend NASCAR Drivers..)
3. How cool does it have to be just to get around in? (If a chick digs you and your ride... GREAT! If she digs you just for your ride... FORGET HER!)
Be realistic. Have a goal and make sure you set aside the time AND money AND have the place to get it done in.
Good Luck and AMEN!
*steps down*