I had a weber (28/36 i think) on a 1300 gls back in the day... it went really well....but also drained the tank very sharpish.
Had many on strombergs and find them to be most forgiving in regards to drive-ability and economy, fairly easy to set up as well, just screw the jet in and out till its right...to be honest they don't need much more than the initial set up and you're good to go.
The zenith downdraught is also a pretty good carb, a good clean and a service and they do the job, I've not had much experience of the weber version, except on escort pop plus' way back in the day... and they were mostly junked in favour of the weber twin choke, which suits an escort down to the ground.
A viva likes a more 'civilised' carb in my opinion, simple but effective, those weber ruffians are more for the boy racers. . . .
(says the guy whose just painted a massive mexico styley white stripe on his 4 door
)