For this sort of problem you need either really narrow nuts... or spline drive nuts?
Narrow nuts tend to be Japanese Aftermarket... Buddy Club, Rays etc. and quite expensive...
Spline drive nuts however... can be quite cheap... I got mine for about $30 whole set and they're still holding up well
Someone recommended me these a long time ago (sorry but I've forgotten who it was... but to that person... thank you! they are still holding up great)
Link to Nice Products PageI'd recommend the 6 point spline because you don't have to carry around the key with you... if you're not worried about the locking anyway
Any Repco should be able to get these in for you