i think that you should do a little bit more research, or start, if you're really serious about doing this project, expecially if you have to ask if your internals can handle the stresses of a forced unduction setup. anything not meant to be turboed aren't made to have a turbo bolted to them. you can't rely on a DD with a turbo setup wiith stock internals if your expecting big hp gains, if you're just looking for 30-50hp gain on low boost, then maybe just a snail would be appropriate and a stock block might do it for you. And power gains isn't just measured on the size or price that the turbo you decide to get. you have to put in time and money to tune right, and unless you're a skilled professional with your own dyno, then i suggest taking your car to a reputable shop to get it done right. but you can definitely find turbo hits lower than 4k, check out synapse, greddy, and rev hard. they are companies that i know that make specific turbo kits for b-series engines. then there comes your internals: forged pistons, sleeves, rods, cs, cams...etc. then theres bolt-ons like injectors and fuel pumps, and these are just among the important mods you need to consider in order to build a reliable setup for a DD, although some of the stuff i listed might be overkill for a DD, its better to be safe than sorry imo. do a little more research and you'll learn alot