I'm very sorry Robbie,
You asked a further question about Albion gearboxes for your Excelsior and I completely missed it. I only found it when I was idly looking back through the old forum topics.
Albion gearboxes are very tricky but not in the way you expect. Albions made a vast range of boxes, particularly at the lightweight end of the market. The big issue is not the actual model of box but the chain lines.
Chain lines are the distances from the centreline of the box as it sits in the frame both to the centreline of the drive sprocket and the centreline of the clutch sprocket.
Albions offered alternative chain lines for the same model of box. This means you can find what looks to be the correct box but when fitted to the bike either the clutch or the drive sprocket doesn't line up with the sprocket at the other end of the chain.
This can be so confusing that I have made myself a simple tool to measure what the chain lines are on any Albion box I come across. This is simply a 12" square piece of MDF with two holes drilled in it to take the mounting studs of the gearbox and a series of fine lines drawn across it marking the centreline of the box and all the optional centrelines Albion offered for both sprockets.
I just plonk the box on the square with the mounting studs through the holes and then see which line the sprockets lie on. Very crude but it works.
As you can gather from all this, explaining Albion gearboxes involves a bit more than can be tucked in here. They are no problem technically when you get to know them. It is the oddball unexpected stuff like chain lines and kick starter variations that throw you.
Cheers, Bob