Armed with my technical docs, I have attacked the truck with Knowledge and the power of carefully directed violence!
Contrivance Extracted, and cleaned and freed off, and reinstalled...
...and it binds up when reinstalled. So more cleaning, and scraping, and scrubbing, and cleaning, and...
it still binds up when reinstalled fully. Possibly the housing is distorted? It was incredibly difficult to remove the mechanism. And it only binds up when it's fully seated...
Anyway, then my other boss got back in, saw me refitting this mechanism again, pulled a face like I'd grown another head and said "Just replace the fucking turbo"
So we'll see whether or not the customer thinks the truck is worth putting a turbo into, at this point! (Probably not.)