I know it's boring, but have you thought about selling the 2ltr to buy an st170, as most of the parts you'll probably be wanting to fit are already on the st.
I've been really interested in fitting an st manifold, and would also like to uprate the brakes, suspension and interior, which led me to thinking that an st170 would probably end up being the cheaper option in the end.
I know this is only my first post,but I'v been reading quite a bit on the forum, and do know a few things about mod'd/performance motors, so please don't give me too much shit.