I would like to format an SD card to fat32 with 64kb Block Size. Disk utility seems to do use 32kb by default and there is no option to change this. Is there a terminal command to do what I want to do?
To format a disk with custom (FAT) allocation block sizes use the -c option with e.g.
sudo newfs_msdos -F 12|16|32 diskXsY. -F is the FAT type (usually FAT32 here).
First get the disk identifier with
diskutil list and the block size of the disk with
diskutil info diskYsX | grep "Device Block Size".
To get the -c factor divide the wanted allocation block size by the device block size: e.g. 65536/4096 = 16. Acceptable values are powers of 2 in the range 1 through 128.
Assuming the device block size is 512 Bytes in your case, the factor is 65536/512 = 128 and the resulting command is:
diskutil umount disXsY sudo newfs_msdos -F 32 -c 128 diskXsY
-v name option will also add a name for the volume.