Realistically I think going from what iv seen over the years being on forums and into cossies, 400hp is about the safe limit some people have had more hp and they have lasted but I wouldn't fancy it! I'm in a similar boat with my Capri, I spent a fortune building a new engine on a 205 block, but then bought a 200 block! So for now I'm going to bolt a t38 on it and hopefully it will last for a bit at around 400hp.