If it was me I'd start with the $6K, and work backwards. You need brakes. You need wheels. You do not "need" hydroboost but yes - it's a fun option to have assuming you have the rotors behind the new blingy wheels. $6000-$1650=$4350. You'll need an alignment too - $150. Wheels/tires/lugnuts? - $2000. You're down to $2200 but it runs and drives and looks cool. So - for the 318... Go find any year running Magnum 5.2L under 80K miles - $400. Buy the RPM Air gap, carb, and air cleaner - $600. Gaskets to swap over the parts and add the fuel pump drive to the camshaft - $200. With the last $1000 have a nice 2.5" exhaust bent up for it with decent mufflers.
The 5.2L Magnum will be close to 275hp as spec'd there. If you want more go with the 5.9L magnum if you can find one cheaply but you'll also need the B&M conversion flexplate for it. That engine will be a touch over 300hp in that form in your car.
With your next $200 buy the ignition recurve kit and a shift kit for it and go have fun.