Welcome to the forums.
My recommendation would be build it with whatever you have on hand or buy a cheapish (105 or maybe Sprint/Cyclone level) to build it and testy ride it and see how you like it. Unless you've had a mid '70s Italian bike it would be IMHO foolish to spend a lot of money collecting a lot of period correct parts only to discover you don't like the ride. You could always rebuild the donor and resell it and pass the Masi along.
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“One morning you wake up, the girl is gone, the bikes are gone, all that's left behind is a pair of old tires and a tube of tubular glue, all squeezed out"
Sugar "Kane" Kowalczyk