If corrosion isn't a problem could you use a steam cleaner?
I don't mean a pressure washer either but an actual steam cleaner.
There must be some type of cleaner around you could drop the intake into. There was a thick liquid carb cleaner that came in metal buckets you could drop a carb into but I can't remember the name.
Seemed to do a good job cleaning aluminum carbs.
If you had some new stuff it could clean a manifold?