Yes I use standard 750 needles. But the American needles and jets are different from the European ones.
The 155 jets you have are not from Dynojet, because they do not exist, DJ makes jets in 2-size increments. There is 154 and 156 but not 155.
As far as I know Factory Pro make a jet kit for 38mm carbs on an 1127 engine, might also work on a B12. Or maybe they already have a jet kit specifically for the B12. Worth asking them.