I do not currently have a built thread, but since you're asking I might as well start one. Better late than never!
The thing about boosting 1UZ motors is that you must have passion towards Toyota's 90's engineering. If you love the sound of Japanese V8 precision and you have the patience and money for all the custom work then go for it! I didn't build this car, I bought it with all the piping in place, and I can see how much work was put in to it. If I remember correctly, it cost the owner before xboostx something in the range of 7k to complete the turbo kit alone. The engine is stock aside from 92-94 internals. Early 1UZ engines can hold up around 12-14 pounds of boost safely which should make near 400HP, very similar to what stock 2JZ-GE engines can hold. Building a 1UZ will cost you at least three times as much as it would cost to build a 2JZ. But with a built 1UZ you can hit 1k HP on less than 30 pounds of boost, it has been done, it's just rare, expensive and time consuming. Dropping a 2JZ-GTE isn't a cure for everything, but you can make much much cheaper power that way if that's what you're looking for. Even dropping a built LSx will cost you a lot cheaper, but I don't even want to talk about those engines or whatever they are.
The 5-speed swap on the other hand is a bit more self-explanatory if you know how to search for information. Although I did not yet find a clear description of an R154 swap for an SC400. I am planning on swapping in an R154 into the black SC I got to replace this abused monster, I'm about 70% complete with sourcing all the necessary parts. I'm trying to do this the right way, no adapter plates or modified MK3 pedals, etc. Once I'm ready for my swap I will definitely get a parts list together, and try to add information that will help/inspire other SC400 owners do the 5-speed swap as well, because let's be honest, 5-speed SC400's are sex!
Although I'm no where near an expert in this field, as for the single turbo V8 confusion, both banks are being boosted if done properly, one side will just receive a slightly lower/higher boost input. The better the piping fabricator is the more equal boost delivery will be, that's what's amazing about this kit, I will take a few pictures the next time this car goes up in the air. Ideally you'd want a twin turbo V8 though, more end game power. If someone is more knowledgeable about this, please correct me if I'm wrong. I got into the game the day I purchased this red SC a little less than two years ago, so I still have a lot to learn!