Front Hub Spacing

I have a front wheel in the form of a 26" rim built to a Halo track hub but the spacing is too small for the forks on my mtb conversion I'm building. The drop outs** fit very neatly** either side of the axle nuts.

?
There should be two overlock nuts on either side of the bearing races.
Remove the outer two, place good quality washers between them and the inner two.