Big difference between 250 and 350 hp. Your stock motor makes 225.
You will be hard pressed to find any quality turn key motor- FI to oil pan- for $3800, unless you look at blueprint, ATK, or some other mass produced engine.
If there is nothing wrong with your present motor, you can put a new top end kit from TFS, AFR on it for about $3000 that will get you to 350 crank hp.