ok.. I hear, ya, most of the other replies didn't. Probably because my favorite engine is a 305, and I build them to drive to work, not drive on the track. Also, I am probably closer to 17 than they are..

To get the lope ( lope is the word for that lumpy idle sound you want ) put in a bigger camshaft. don't go above .454 lift and you won't have any problems. I'd recomend a .454 lift intake and exhaust, with a 290 duration, intake and exhaust. I think Comp cam has that one. It is in my firebird, and I really like it. Fuel economy is good, about 18 MPG @ 80 MPH. To install the cam, you'll have to either yank the motor, else pull the radiator, and all the front metal. the cam is long, and you need some room to work it out. You'll also have to get a gasket kit, as you will be pulling the intake and timing chain cover. Would be a really good idea to replace the timing chain at least... pretty cheap and since you are in there... under $15. You can accentuate the lope by fine tuning your timing and idle speed. Something to consider... when you have it really loping ( thubba-tub -thub- thubba ) it will tend to kill out in sudden stops and such. You can compensate for that by throwing it into neutral.

Some other parts to consider, without breaking the bank..

get a performance timing gear set, and set it for your prefrence, low end torque, stock, or top end. under $50. Do it when you do the cam.

long tube headers. Will give you low end torque, fuel economy, and they sound great. under $100.

cherry bombs ( glasspacks ) will give you that awesome idle resonance, and still keep you legal, and they are cheaper than flowmasters. See if you can convince a buddy in auto shop at school to do the exhaust mods for ya.

good luck, and above all... keep it streetable.