It would appear my question has sparked some lively debate around this topic, which is a good thing as I've learned quite a bit.
I am unashamedly a 'stick the car in a field and polish it' owner, if you've seen my car that will stand to reason. But I do like driving it hard when the opportunity arises so I'm not looking for sparkling performance just an improvement on what I have, which at the moment is a knackered gearbox. I am going to go down the road of swapping the box probably to an S13 as money is as always a factor and £600 plus notes on the box alone is not an option for me. Having done a fair bit of searching on the topic I am still left with some areas that need some practical answers.
What mounting mods will need doing, is there a pattern so I can copy it?
Is there an issue with the speedo, not seen anything to suggest there is but will the existing cable and drive work? If not how do it sort it?
How much do I need to shorten the prop by, having just paid for one to be made I don't want to bin it.
Machining the bell housing seems straight forward however, as I found a good article to help me with that and I think I can now do that my self.
So any of the above that can be answered I would be grateful, I do intend to make a few calls on people mention so far anyway.
Thanks again for the advice so far.