Jeremy,
Earlier this year I did the Solvang Century on a '85 Pinarello Montello. Comfort depends mostly on tires and saddle. I did the ride on Continental GP 3000 that I found harsh. Vredestein and Veloflex ride better, both are available in period correct gum - black. Tubulars I've not tried but are said to be lighter & even better riding.
Compared to a 20sp modern bike there is the challenge of finding comparable gearing. For that ride I assembled a 6 sp Regina Corsa in a 12-27 in anticipation of the 'wall'. With a 42T chain ring that FW gets you close to a modern 39-25.
Compared to a aero wheel modern aluminum frame the old frame are likely more comfortable.
Paolo sant'ambrogio
Santa Monica, ca
'85 pinarello montello
'03 mondonico foco