i don't know if you can get anything off the shelf for this application? but from my own findings and experiements of many years ago; a pair of short solex manifolds off a t3 would be a place to start. those carbs won't fit straight on, the studs are a little wider for the manifold holes. but you could easily get them to fit etc. also you'll probably need an early style fanhousing, as the carbs will foul the lower sides of the fanhousing. also the jetting will certainly be wrong for a 1600, no idea about the availability of jet sizes, though from memory they look the same as many motorcycle jets, so somehting could be figured out.
to be honest it all became a load of hassle to me really. in the end of fitted twin pdsit? carbs of a 1600 t3, bolt straight on, no clearence issues and minimal mods to the linkage and your away; nice response, good mpg return etc. definately worth a though for cheap(er) route to twin carbs. you can normally get them at vw jumbles for not much. i got a complete set for a twenty quid, though useable i have them for spares for the ones in use.
cheers.