yeah i dunno man i don't actually know much about the whole turboing a 4k-c thing but i'd be inclined not to bother. I just don't think a 4k-c is the right platform for that kind of deal, I'd just put a 3K head on it maybe port and polish if you can, extractors maybe. I don't aspire to do much more than that to my 4k-c, i'm saving the money for something with a bit more potential, but go for your life if you want.
By the way I made a start getting the 3K head out of my ke20. Man rust is a bitch, the bolts are all fused, I've used a fair bit of RP7 but no progress at all yet lol.
But yeah it'd be cool if you did turbo I guess, entertain me! :D