The DOHC would handle boost awesomely. As for those headers, don't waste your time, they don't fit right and you have to do a lot of other work, just to get them to fit.

Not a lot of mods you can do to a 3.4l DOHC. If you can find heads, from a 5 speed car, swap those in as they are higher compression, put a cold air intake on it, do a custom tune.