Websites like Paddocks Spares or Rimmersbrothers offer comprehensive parts catalogs for Land Rovers. You can browse parts diagrams and compare them to your photos to potentially identify the gearbox model.
Loving the dedication, BikerB! I also looked here. NOS valves and stellite exhausts? You're building a museum piece! Keep the updates coming, and let us know when you find that elusive machine shop for the final touch.