"Speed costs, how fast do you want to spend?"
Unless you are looking for a dedicated race car, you should really consider just working with what you have now. A second street car has indirect costs for insurance, plates, maintenance, etc. A dedicated race car needs a trailer, tow vehicle and insurance should be considered.
As stated, 11.50 makes a pretty natural cut between street car and race car. Sure, street cars can run quicker, and race cars can be driven on the street. But at 11.50 you are quickly compromising your street manners. You'll need 4.10 or deeper gears, slicks or DOT drag tires (short street life), safety equipment, and creature comforts like heater, wipers, back seat and such usually go away. Chassis tuning for street handling and drag strip performance is diverging at this level.
The Duster in Vegas looks like a fair deal. It's a factory 340 car so the body has some value. But it has been tubbed and 4-linked which hurts the value for restoration, and is probably overkill for a, 11 sec car. That chassis will support more power down the road so it's a package that can be grown into. $30K invested? Maybe, but it could be done for less.
What does your car run now? Do you race it regularly? Is that your goal?
$1000 should get you onto the track with 4.10 gears, a set of slicks and subframe connectors. Add another $1000 electric fuel pump, a Holley 3310, and a 150 HP plate type nitrous system.
.
