On a classic , wish I hadn't lol

Got the downpipe off , now need the 3 Nuts and 2 bolts/nut , anyone know the spec of these or where to get them ?

Anyhoo , can't remove any of the up pipe bolts , seems they have shrunk lol , not quite 14mm nor 13mm so with s 14 mm they just round off a bit , 13mm won't fit . I've used s blow torch as well

I was thinking can you remove turbo with up pipe on it ?

If not only kind of option is scree on another nut onto the protruding thread and weld to old nut , clasping at straws tho !!!!