True, and most bearings and quite a few lip seals are generic so will probably appear in someone else's 'boxes.
Ford, for example, donated most of the parts that went into these very rare Reliant "long" boxes from Rebel 750s, the only car to use this exact device! You would be unlikely to find a bespoke gearbox in any modern car that was only built in quantities in the low hundreds:
I was sufficiently single
at that time to get away with using the kitchen for these tasks, old pal and fellow Kitten Reg bloke Mr P flew over from Dublin to do the donkey work on that one with me. I say "with", I cut some fresh gaskets out for the gearbox guru in the images to use when he reassembled the box later that morning. About 3am I believe it was when we'd finished. He did the hard, physical stuff that involved lifting and swearing. Shame you're so far away or I'd ask him whether he'd quote to build yours for you. And no, it didn't start that clean..
PS: I've seen new clutch carbon thrust pads that had become detached from their carriers as a result of poor storage in damp conditions, they go quiet when you depress the pedal since they're then held still by the clutch and the release fork. It takes no great time to check it once the box is out, though Harvey does as ever make a very good point whereas I tend to eliminate the cheapest jobs first!