OK, oftec have the position that you should use the nozzle which the manufacturers used to get the boiler type approved, but that AFAIK will be for recent boilers, as type approval was not about for the older ones.
There will be a nozzle in the boiler when you get there, and that will give you some analyser reading. If you can get around CO2=11% +, and CO<50ppm, with no smoke there's no problemso you an use the same nozzle for replacement. (You could also say "everything is running fine, so why waste the raw materials used to make another nozzle and change it when it's not necessary).
It's perhaps the nozzle angle that could give more problems, but a look through your records will tell you that, as almost certainly you will have done one before.