From the part catalog, it looks like the steel tube is integral with the carb. If it is not repairable, I would guess it is a press fit into the carb body.
The crossover piece is item 8: Allbrit.de - Ersatzteile für LAND ROVER & MG ROVER
Part 612505 for the pipe with olive 614555 and nut 534790. All cheap and available parts.
You could also easily replace it all with a few fittings from a hardware store. A couple of tee compression fittings and tubing. It is probably all 3/8".