Width at nut in relation to string spacing. advice needed :)

Im new to guitar building and im currently building a custom telemaster and i was wondering how the string spacing affects the width at nut, i have a 54mm string spacing would this require a 43mm nut? Im just curious to know because im deciding which neck to buy.
Thankyou

Teles (& strats) either get a 42mm or 43mm nut, there are some odd-balls with narrower ones,

Personally I cut my own from bone blanks. What string spacing you use then depends on your preference. I like the top E to be a little further onto the fretboard than normal so I do not pull it off the edge. Then the bottom E must also not fall off the edge. This sets my two outer position, I then mark the middle slots equi-distant with calliper and engineers dividers, I do not compensate for string width. This does mean the gaps between the treble strings is greater than the bass side, but this is better for fast leads on the high strings and chord riffs on the bass.

One thing to watch is that the strings must pass directly over the centre of the poles in the pickups, there are dead-spots between the poles. So it is the pickups that effectively determine the required string spacing. especially at the bridge. A blade pickup does not present this problem.