All legit and very true k3:18s max IMO. Driving style and road conditions will play a huge factor in on your transmission. As stated these transmissions aren't the best to begin with. Your transmission isn't the only piece to the puzzle either. The added weight will also put a strain on cv axles and all other suspension components. Research will also show that the ride quality and comfort will suffer from running 20s. I would also look for a drop in power and mpgs with the extra rotating mass. Tires will also be more expensive, and brakes will wear out sooner too.
That being said its your car and your preference. Some people have had no issues with them, some have. Best of luck, scotty.
They can be hard to find for sale. My best suggestion is to check Craigslist in US cities that are close to the border, and if/when you see a set pop up for sale at a reasonable price, take the trip downyeah I want those ss wheels but out here in Canada you don't see them for sale often and when you do they go for $1000.