A properly built Dart longblock from an engine builder capable of handling 800+ hp will run you around $9k+. Then you still need to add all the top end parts, accessories, and a power adder. A Dart 363 with methanol and a PT88 will push you close to the 1000hp mark. I'm building a Dart 331 setup (RNH longblock) with meth and a PT76 that should be in the 700-800rwhp area. To be realistic, your budget of $15k won't be enough to even cover the entire engine/power adder with all supporting accessories. $25k is probably a more realistic budget. I have an excel sheet with a laundry list of parts that I need. The list still has $15k worth of parts left, and I already bought the engine, transmission, and have a shell that everything is going in.
Putting that much power is a car causes a chain reaction of money spending, and it all adds up extremely fast. You have a 1000hp engine, but you need to tune that engine. You want all that power to get to the tires without tearing the car in half, so you need chassis modifications. Your drivetrain will also need to be completely rebuilt. Brakes will need to be upgraded. If you want to legally run 9's at the track, you'll need a whole slew of safety upgrades including a full cage. It goes on and on and on. Good luck!