The Gotoh GE101 has a steel block, according to their catalog.
The Gotoh/Wilkinson has a steel block, by hearsay.
The Fender Am Standard is anybody's guess. My guess would be zinc.
All three of them use cast saddles, rather than the junk stamped steel parts Fender used for so many years. On the Gotohs, they're stainless. I suspect they are on the Fender as well. Also, they all have hardened steel mounting plates. So, they're all fairly similar. Given a choice, I'd use the Gotoh/Wilkinson.