Start by getting the Demon Tweeks motorsport catalouge... The Pacet fan range is quite large.. so find the size of fan you need (cant remember what size ive got, but theres room for a larger one!!!) The fans are very slim, the depth of the fan fan is much less than the standard one, so should not pose a problem with the manifold or throttlebody!!!
Cant remember the cost, and i fitted it myself!! You need to work out a method of fitting it, using the holes in the radiator.. use the fittings supplied with the fan... and a little work connecting it...
Michael