The width is 1600mm. I have a K27 which is 1600mm wide and bought 2 of these bridges before the loco.
An angle grinder down the middle made them much wider, very quickly and I planned to fit new cross members to restore the strength, but tried the sides fitted on my supports with track just laid through, to test.
Surprisingly, the bridges took the load of the loco and train without blinking, so I never fixed them permanently.
I have since moved them to a less visually important place because impressive they're not.
What you are building sounds very impressive, and these bridges could just spoilt it for " a ha'porth of tar"
That's just opinion though, the strength of the bridge is a fact. John.
I replaced with bridges from this guy www.mvlbridges.co.uk
You get product built exactly to your requirements, but they are dearer. You get what you pay for of course, but one as a centrepiece of your creation would certainly look impressive. ( No connection, just a very satisfied customer).
HTH