Version relates to analyzers and the like rather than to internals
such as index format. I don't recall what exactly has changed between
4.0 and 4.3.1 but you're probably safe to change it and use LUCENE_43.
Take a look at the javadoc for StandardAnalyzer - that lists some
versions and what change
I'm relatively new to Lucene and am in the process of upgrading from 4.0 to
4.3.1. I'm trying to figure out if I need to leave my version at LUCENE_40 or
if it is safe to change it to LUCENE_43. Does this parameter directly
determine the index format? I have some existing indexes from 4.0 but
