After having had both, I prefer the 60mm for "primary" gauges. They're really not a whole bunch bigger, all things considered, but they typically are a bit clearer and easy to read.
Not sure on the FD's gauge pods, but the FC A-pillar gauge pods could EASILY be opened up with a Dremel to fit a 60mm gauge. Takes all of 5 minutes, and the end result looks great.
Also, the pods that go where the center speaker goes come in 60mm versions -
Dunno about the RE Amemiya style steering column mount, though.