Yes, City Spring is good - I had them replace my boat trailer axle
many years ago, standard leaf spring.
I bought a torsion axle
from Standens in Edmonton for my Trillium
4500. They were easy to work with as well - they have an on-line order form to help out.
I can't remember the dimensions and angles that I used, however. Can't remember anything, unless it's REALLY important, like the words to Us and Them by Pink Floyd...