Evening! Thought I’d report back to close this off. It’s done, and works! No crunches up or down the gears, hi and low all good, 4x4 good, overdrive works great… no odd noises… so pleased..
I ended up changing a few things at once, which isn’t normally the way as you never know what change solved it, but I wasn’t going to keep removing the box to each change.
I replaced the 3/4 synchro hub for a genuine new one.. (remortgaged for that), replaced the alleged genuine layshaft with a proper genuine new one, the difference visually was interesting, with the reverse teeth rounded to receive the idler… and whilst in there, popped the original synchro rings back in as they were in fact still in good condition and well within tolerance. I replaced the Layshaft bearing & race and ensured correct clearance, using a smaller spacer.
I have ended up with a very expensive rebuilt gearbox. Everything, I mean everything is nos genuine parts, other than the baulk rings… ironically. But, it’s perfect now!
Hope it’s useful to someone. If anyone needs any suffix A gearbox parts, I might have a good serviceable one of what you need in the box of what’s left, just ask!