Considering Ivan's triple query, my questions are:
a. How mint & original is your Doniselli? My Austro-Diamler and Frejus "hot-rods" weren't in good shape or not a valuable collectors bike to begin with. If it's worth something, you might not want to start messing with it. If it's your favorite bike, but it's too hard to ride anymore, and you want to keep it forever, then go ahead.
b. Is the Doniselli a short wheelbase racer or a longer stayed tourer? As Jerry Moos said, a short stayed bike is harder to triple. Any touring planned, or just day riding?
c. Do you do your own wrenching on it, or take it to the LBS? My experience, if I do-it myself, I can make anything work (...yea, right), taking it to the shop, they're going to throw parts at it and it'll cost a bundle.
d. Do you want period-correct or all Campagnolo components or would a mish-mash of parts do? You could shop around at bike shops & swap meets for take-offs or low mileage modern components at bargain prices as compared to rare high-priced 60's parts that don't work as well.
e. Would you want another bike, or space/mood constrictions limit you to 3 bikes?
As for me, I'm going through a catharsis with my bikes too. I became interested in track racing this year, and found out I liked it. Plus work changes precludes much time off, so I can't take that long bike tour I was planning. And my daughter has grown to a point where she needs a full sized bike now.
I found a well used Cinelli track bike that really trips my trigger, and the owner is willing to part with for less than I guessed. My town bike got converted back to an ATB for her; I've put my touring bike and bags up for sale; and I'm getting my Vitus 979 ready for sale (only need one retro-racer at a time). So out go three bikes, so one can come in.
Roy "still recovering from a week in NYC" Drinkwater Lititz "another long ride today", PA