feck me thats a tidy looking engine, nah 250 will do me nicely 
im not familiar will all the technical stuff just yet but it wont take me ong pick it all up. where can i grab a k04 from? any ideas
250bhp you need a very small frame turbo, any k04-001, k04-022/023 or hybrid k03 will be fine... I was anticipating true madness from the title of the thread.
T62R madness... 

Most of my relatives run GTX35 at ~2bars making a streetable 7-800bhp so I was expecting double that 
That's not anyone I know, was a customers car at my mates garage, no one I know personally runs t62r...
You can pick up a k04-022/023 on eBay - used if course, just make sure it's genuine. Personally if you're going for 250 I would just get a hybrid k03, I recommend beach buggy turbos. It will require light bolt on mods and mapping but it's less parts that need changing compared to if you went k04-022/023
Sure someone has posted a list before. Every engine is different and just because one engine makes 250 bhp another might make more or less with the same mods. Better to focus on how it drives, but the usual mods are things like decat, downpipe, catback exhaust, turbo intake pipe, uprated fuel pump, front mount intercooler etc etc