I don’t get this reluctance to dismantle the carbs expressed in this thread. Talk of stripping threads for instance, there are 8 screws holding the carbs onto the bracket, the threads have probably never been touched since the carbs were assembled by the manufacturer, little to no chance of stripping those threads. The ones that do have some risk of stripping are the float bowl ones and you’re going to need to take those out whatever way you decide to go.
Dismantling the carbs gives you a chance to clean and inspect areas you can’t really get to when they are assembled, it also allows you to access the fuel banjos, something you’re going to need to do in order to change the orings, or were you planning to change all the others but not those? If so were you really comfortable with changing all the rings to viton but leaving them as nearly 50 year old Nitrile rings?
Taking them apart can seem daunting, I get that, but it’s easier than you think and gives you a better understanding of how they work. Do it logically, keep all parts of one carb separate from the others, use numbered boxes for instance, use another box for the parts for the bracket and the throttle mechanism, if worried do 2 carbs at a time, say 3&4 so you can check 1&2 to see how they go back together. Without taking them apart you can’t check parts like the felt washers, 7 of those on the choke mechanism and 4 more on the throttle lifters, you can fix problems like rust forming on some of the mechanisms.
I’ve done loads of these types of carbs, I’ve done so many I don’t need to check where parts go, be meticulous and pay attention to how parts work before pulling them apart, if need be take pics or follow a good online video, if stuck ask. Reassemble using lubricants and you’ll find them easier to operate afterwards.
Putting them intact in an ultrasonic bath is asking for problems, you can literally shake stuff like the felt washers apart doing that, they ain’t the most robust things in the world to start with. Besides causing the steel parts to rust afterwards. There are plenty of steel springs hiding in the internal mechanisms which will suffer if not removed before you put the carb in the ultrasonic bath.
If you find you need new felt washers drop me a PM, I make both the choke and throttle lifter ones for a very cheap price.