The stock Honda front caliper has two 30mm pistons. V65 Honda's used 32mm pistons, which will fit directly onto the FT caliper bracket.
In the rear the stock FT caliper has 27mm pistons (at least mine does, even though the manual says they are 30mm?) The front right-side calipers from several '82-'85 Honda's, such as the 650SC, are 30mm, and will fit directly onto the FT rear caliper bracket.
All the 30mm calipers I've seen are marked 30, as well as the 32mm calipers I sourced from a junkyard, but the stock 27mm rear caliper wasn't marked, and I found at least one unmarked 25mm caliper while rummaging through a pile of calipers at the junkyard.