Did you start from Larn 12.3 or 12.4? Did you get the source from larn.rogueforge.net back when it still existed? Is there a complete diff of all the changes you've made? Do you plan to make changes to the gameplay as well as the interface?
I started with 12.4alpha2 as it was easier to port back to *nix systems than 12.4.4 was. I fixed a whole load of bugs introduced in 12.4 onwards and then patched in all my changes into 12.4.4 (which was the last maintained version in 2010). I've also ported code from 12.3 and 12.2. I've never seen a 12.1 or 12.0 Looking at the history they were limited releases.
I got most of them a while ago from http://lactose.homelinux.net/larn/
and sent in my fixed 12.4alpha2.
Is there a complete diff.. yes and no. I updated the original changelog that came with Larn with what I've done. But because I've indented all of the source files, false diffs are everywhere. Many of my changes contain comments with '-Gibbon'.
I plan to make gameplay changes 'only' where they are needed for balance etc otherwise I'll keep it as 'original' as possible. I've actually made a few changes already (Lance of Death is now Great Sword of Death and it is +24 not +25) since you'll have bumps by that time. I've also doubled it's price. Interface changes will be very minor, I'll make text at the bottom reach further as it is quite a small space and add color (way way into the future). Right now it's mostly back-ground changes, like moving declarations into 'real' header files instead of the current 'everything in one file' approach.
By the way, I also maintain an XRogue fork at https://bitbucket.org/ElwinR/rl. Feel free to copy any bugfixes.
Nice to see someone other than me is doing it. XRogue gets very little love these days, I'll take a look.