^ You get a 2.0 or 2.4 DOHC. The 2.0/2.4 are identical except for the deck height of a 2.4 is roughly 1" taller, rods, pistons, and, crank differ as well but everything else interchanges. SRT4 power is the answer, SRT4 power is always the answer. Here is my easy 300hp 2.4 you should be able to put this together new for challenge money, used for damn near free.
95-02 2.4 (look in Stratus, Breeze, PT Cruiser, Caravan, Voyager)
OE Mopar SRT4 Pistons, Rods, and, Rings(Forged will deal with 500hp well tuned if the revs stay below 7k)
Neon SRT4/PT Cruiser GT Turbo: Dinky, cheap, and, easy to find, you may as well find one with the oil and water lines attached because they will work on an earlier 2.4. IF you can find one the turbo and manifold for a Mexican market Stratus R/T Turbo is preferable (T3 Flange and much larger than the TD05)
Forward Motion, AGP, or, Mopar Stg2 wastegate actuator
Gvalve style boost controler
3" o2 housing and downpipe
Now we come to the hard part I usually say 750cc injectors and megasquirt (we used the older block for the older crank sensor that megasquirt understands. I dont think there is megasquirt code for NGC 03+ engines yet) but the injectors are spendy usually over $300. Stock 04+ SRT4 injectors will deal to about 18psi which should be 275hp 320tq. 750cc will do 21 psi(the turbo cant do much more) and over 300hp 350tq
Its really hard to hurt the engine at these power levels my SRT4 has 110,000mi set up like this easily 30,000 track miles and its just as good as new.
Easier cheaper way is using a 2.0 DOHC neon engine with the SRT4 manifold keeping it around 8psi should be let it live you will just make 200hp if tuned well. Do not let it detonate. Do not exceed 7000rpm
Old 2.2/2.5 with a big swingvalve, exhaust, +40s and more boost will get there too but I have awful luck with 2.2/2.5s