Radium as mentioned above used to make a full bolt on kit. Might want to reach out to see if they still do though I dont see it on their website.
The other company is Monkey Wrench Racing.
There is nothing outside of those two companies unless you find a used kit.
Depends on what you want. There are no prepared kits I am aware of. A turbo will always be more efficient than a supercharger. Depends on use and how deep you want to go...I am doing just under 500 whp on a turbo k swap and could easily add a couple hundred more if I wanted. It’s rather quick as is