Having done a search myself, the only thing I've come across is
The Terraria Seed Project. Sadly it's nowhere near as efficient as TerraCustom.
The reason there's not a bigger push to port everything to 64bit is because vanilla Terraria can't support 64bit. The engine Terraria uses, XNA, was made before 64bit support was even needed by most people. As the engine is no longer supported ReLogic would have to either port the game into a new engine or do the conversion themselves. Either situation would be a gigantic nightmare, and the results would take so long to produce that you're better off just making a Terraria 2. I think ReLogic has already chose this route after the announcement of Journey's End.
TMod 64bit is not the perfect solution either. The loader itself is not completely stable and has bugs unique to it. Also many mods need to be modified to work with it, meaning a mod developer would have to either drop support for TMod 32bit or double their workload. There's no good outcome there.