Also I'd be really clear on why you want to use ext3 over ext4. Ext4
has numerous advantages over ext3. This article "rm -r fs/ext3" is
kinda interesting:
https://lwn.net/Articles/651645/
Basically these days it's the ext4 kernel code with backward
compatibility mounting an ext3 file system.
And you're almost certainly best off just using the default mount
options, again unless you have a specific requirement and understand
the consequences of non-default options. The non-default options are
just going to make your file system more non-deterministic in behavior
compared to the upstream testing that happens which is heavily
weighted on default mount options.
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Chris Murphy