3-0 or 3-1 Fed. Clear as day. When Cilic blew Fed off the court in the USO semis (and he literally blasted him off the court) he was not facing the newer Fed, which is the one we saw all of last year. In 2016 Fed faced Cilic again but this time in Wimb. He came back from 2-0 sets and resolved those demons.
When they played again in the Wimb final of 2017 Fed just dusted him off the court, and the result would've been the same w/ or w/o the blisters. The match they had in London a few months ago was like a meaningless tie, but Cilic went all out. He managed the 1st set in a TB, but then was schooled in the following sets.
Given the strength of his serve, you could see some higher sets.... but i'd guess
6-4, 7-6, 6-3
6-4, 7-6, 6-3, 6-4
Fed wins