There are more than one width for 18RG manifolds. If someone tries to sell you linkages, make sure that you match the length of the manifold they come off to the one you have.
Any manifold of runner length 60mm from centre of head flange to centre of carby flange will take the same linkages I reckon, of will be easily modified to work.
Manifolds that have a head to carby length at the runner centre of 90mm should have linkages compatible with other long manifolds.
I don't have a digital camera so I can't get any photos to you, otherwise I would, sorry.