Whatever changes are made to an engine will affect the choice of needles. Whether it be valve size, compression ratio, restrictiveness or otherwise of the intake system, back presure of the exhaust etc etc. It is therefore a very brave man who guesses the profile of a needle without seeing that particular engine and ancilliaries on a rolling road. The best that Ron and I and all the web pages in the world can do is to make a stab at a likely solution which will allow your engine to run sufficiently well to tide you over until you see it on the rolling road. Once there don't try and second guess the outcome - you're likey to annoy the guys setting your up engine intensly!
The point of going to a rolling road is to be able to collect data that is not available to you under normal or even expert amateur circumstances. And to be able to do this under loaded conditions. Given this data, it is then possible to devise a new distributor advance curve, and needle profile - not necessarily from within the range sold to the public.
There is actually no need to ask for a particular bias towards racing, torque, fast road etc. Generally - although as with everything in engineering there are exceptions - the highest power / torque (they are the same thing: power = torque X engine speed) will also generate the best economy and responsiveness. The exceptions do though relate to petrol engines, where a fuel air ratio in excess of the stochiometric will generate slightly more power. but this effect is minor. For a diesel the relation is pretty well absolute, which is why the most powerfull diesels are also the most economical.
Ergo - don't spend too much effort choosing a needle to get you started. Concentrate on getting it to the rolling road as quick as possibe. They are surprisingly cheap, and I'm certain you will be astounded by the result. When we did Lucky we raised power at the back wheels from 62 to 112!
In the meantimne, concentrate on giving the engine the best chance to generate power. Free up the induction system, either by the method discussed here recently or by the method I used at the start of this thread. Take steps to reduce the exhaust back pressure. (in English, use a bigger diameter system, an extractor manifold, through flow silencers etc) Use the highest compression ratio you think you can get away with (compression ratio defines the maximum theoretical efficiency of an engine - the higher the more efficient and hence the most powerful). Choose your cam carefully for the character of engine you want - all revs? or all torque? Are the valve seats nicely angled? Have you had a go at cleaning up the inlet tracts? Are the ports of the inlet manifolds and exhaust manifolds properly aligned with the heads? Detail is everything in engine building.
If you need any recommendations for rolling roads that understand the engine, I've successfully used a place in the Cotswolds and Quattro has had good experiences with a place in Blackpool.
Best of luck
Chris