The studs look long because the insulators are not in place. The insulators also have the important o-rings in them. The problem with clearance under the frame rails is a problem with any non-standard carbs or longer inlet manifolds on the SF. The later SFC had the frame pressed in, others have cut and shut the frame rail.
dont mess about, just make a single carb conversion using a 40mmFCR pr even a 41mm car type SU
no, never did, but I always thought it a good idea, when an SU was fitted to a Commando (a readily available kit) the bike lost almost nothing, became a lot easier to live with, more economical plus removed one more regular job that must be done, ie balance the carbs, there are today still literally dozens if not hundreds of Laverda riders, on twins and triples who do not posses equipment for balancing the carbs, they dont know what they are missing, there are even others who posses the kit but say that "its not neccesarry" and dont use it. Your twin or triple should tickover for a fortnight without stalling, many will die if at red lights after 20 seconds or so unless constantly "blipped" many triples even start from cold on two pots, the other chiming in 5 seconds later, both are clear signs of unbalanced carb slides, and as for "they all need half choke to start when hot/warm" that IS JUST COCK
I think I still have a twin choke Weber (off an old Escort) knocking around somewhere if any one wants to experiment.Had thought about trying it on an Atlas instead of the PITA Del car carb.
is it a 40 or 45 DCOE Webber Manx Mog? (ie side draught not the horrible 28/36 progessive choke downdraught, cheapo, and actually made under license by Ford?
might be interested if the former, could probably swap it for something Lav that might exite you.
Since both cylinders don't fire together, would a single carb not work just as well as two?

The theorie is good, but keep in mind: to achieve the same power output, you would need a single carb that is much larger than one would be on a "one-carb-per-cylinder" application. This can cause the carb to be so big, that you get in trouble with low-end torque, as there is no sufficient underpressure at low revs due to the size of the carb to get you a good air/fuel mixture or vaporisation of the fuel.

So - to compensate that, you go smaller on a single carb than the combined throughput of 2 or 4 carb applications, which in return can reduce max throughput and therewith max power. See Harley Davidson's or US cars: 5,x litre displacement but only 200 HP or less on a V6 or even V8 engine... They are built for torque though and low rpms.

At the end, there isn't to much of a benefit for single carb applications over one per cylinder on a bike if you look for best performance.

Worked on a 2 carb car with a 4 cylinder engine from Honda end of last year and rebuilt the carbs completely. If you see what the Honda engineers came up with to make this work, I was really surprised... roughly 20 under pressure lines, water heating, heat sensors and many other "gimmicks"... It was a tough job to get everything together again and make it work as it should after ultrasonic cleaning the 35 year old, dirty suckers. It belongs to a friend of my son who took it off the car (13 hours...!!! It would have been quicker to drop the whole front with suspension, engine etc.). When we looked at the other components, I finally found the reason why it ran so lean (Lambda 1,5): 2 cracked manifolds, besides 3 of the vacuum lines with cracks...
My low compression 540 cu in boat V8 was dyno tested at 550 hp on 87 octane unleaded fuel and a single carb. Had I chosen to have it built with different pistons and run better fuel it would have made upwards of 800 hp, also on a single carb.
The 200 and lower hp v8 were the strangled smog motors of the late 1970’s and early 1980’s.