Firstly, gutted to hear about the trouble you've had

If you go the whole hog and go for the new engine, the world is your oyster.

There are so many different opinions on what way to go, it can be a bit of a minefield. There is always a new theory just around the corner as to whats best. The most popular at the moment being the 2.35 stroker.

Then you get into Turbo's and their set ups. Twisted or not etc etc.

I would take the time to trawl through build threads, both in here and on other forums, you will find the one that suits what you are trying to achieve.

I would however, point you toward Midlife2 and his 2.1 stroker (iirc) for a like for like comparison of what is achievable with your car. That is an awesome build and fook me thats got some grunt. Also, speak with James (Anger) his old RA was a proper monster. He will point you in the right direction.

Good luck and keep us informed of what you are doing and post up the rebuild with loads of pics.