It has a larger capacity in chain wrap, so can handle a triple up front or larger chainring difference. However the geometry is the same so it notionally cannot handle anything larger than 27T on the back.
That said, usually you can push things a bit as Shimano is conservative.
Actually I do, the only issue with mine is that is has a different crown, with the bolt-in steerer and missing the two lightening holes. I am happy to do a swap and you switch crown, alternatively to sell you the fork.
If you got a 653 framed Edge for £40 then you got the deal of the decade - a wonderful frame indeed. They don't go for strong money but ride every bit as well as hand built exotica.
Maybe on a good day £150, much of the value is breaking it for parts, frankly. Nobody wants old 26" full sussers with rim brakes.
Apart from loonies like us of course. ;)
Just buy at your LBS or a decent online retailer (ideally LBS) to avoid the (high) chance of a fake. My local guy mainly stocks Taya, and they have given me good service, certainly not significantly different to KMC or SRAM.
Nothing at all to do with the bike apart from the shell width (68 or 73mm), all depends on the chainset. Try the Sheldon Brown BB database.
My guess is 113mm.
As it's so easy for me to get there, I've visited most of the coastal stuff over the years - originally about 15 years ago with sons on the tandem, some photos back on pages 28 + 29 of this thread!