Just when I thought I had seen all the different versions of the heads, you have to come up with another one.
What is the casting date? FB is a 315 hp code and If the casting date is April or May of 58, then this is the late 58 Police Cruiser head.
If it's a 59 date, then it's
cuz the 335 hp should have been out by May of 59 and that would have been a FE code.