if you go KA route you can do it much less then 5500, your going to have around 1k-1,500 in machine work alone, depending on what you want done. my dad had this 4g63t rebuilt at M&m they did an awsome job, they hot tanked everything, finished the head, and put in 6 new valves, decked the head and block, micropolish the crank, put in a bs kit, all new bearings, bushed the rods on the new forged pistons, and put togeher the short block for 1300$ you can do it for far less if you put together yourself, If you need any help with the ka also I have built several over the years myself. They have a group buy on zilvia for Eagle rods, je pistons, bearings, hypertech springs, retiners, +1 mm valves ect should check it out. check out the shop page. Another thing just because a motor can hanle 500+ hp does not mean its going to, making that much power takes alot of other things, like lots of fuel mods, sandalone, and good tuning, that alone is going to cost abit .
fuel injectors 200-400$
frp 100-300$
aem w/ ugo 2100$
fuel rail 100-200$
turbo 800-2200 depeding on size and brand
oil /water lines 300-400$
I can go on and on, then on top of tht If you can not tune your going to have to pay someone to do it for you.