New leaf springs on my 71 duster

I was wondering who sells good leaf springs for my 71 duster currently a slant six car with a 7 and 1/4 but I have a A body. 8 3/4 rear that I plan putting in the car along with a 340. So my question is what are my options for leaf springs? Only thing I seem to find was slant 6 springs or hotchkes springs ... Could I put a leaf spring on it that will work with the 8 3/4 or should I wait to just put new springs on it when I do the 8 and 3/4 swap?