Well thanks for all your replies. Apologies if my use of the phrase 'Samuri conversion' grated on anyone. I don't know the history behind all this and just thought that a Samuri (apart from the body colour) was just a Z that had had a specific number of modifications made to the engine to increase performance.
I would probably enjoy a bit more performance from my car but don't want to do anything too radical and spoil it. I use it every day and needs to be able to deal with town traffic etc. If I wanted the head rebuilt/bored out etc and a different camshaft and manifold and carbs fitted what sort of cost would I be into there? Also, and perhaps more importantly, who would do the work? Fourways? I don't want to take it into some place that then leaves it languishing in its workshop for six months. I would like to take it somewhere that knows what they are doing, who could turn the job round in a couple of weeks.
Then again, I may just decide to leave it as it is as it is running really nicely at present - would just like to knock a couple of seconds off its 0-60 time.
While I am on, can I just ask - is there anyone out there still offering the S14 gearbox conversion - I believe Pmac used to do it? I had my box rebuilt a couple of years back and it is still OK but there are some very small signs of synchromesh problems beginning to return - worn rings no doubt.