The recipe was formulated for the Moro's we see here in SoCal. If the sicilian's you're using are the Sanguinello variety then I suspect the substitution will be straightforward. If you're using Tarocco oranges, from my quick reading, you'll get less color and less bitterness, but I think you'll be fine on the first pass.
(FWIW, I used that much Moro juice cause I had it on hand after I got the oranges for a steal and I was really trying to get a deep color. The beer ended up being the color of a good blood orange soda so an obvious pink.)