I have a 8L90 transmission and looking to swap out the stock torque converter (which has issues) with a built TC.

However, there seems to be no simple answer. I have a 2018 Silverado 1500 High Country 5.3L.

1. Which diameter do I need for mine? There are a few different options
2. Which stall should I go with? Again, more options
3. Do I need a billet flexplate from Circle D?

I don't have a transmission shop in my area, and my local Chev says they won't install an aftermarket TC unless I buy it through them, and they want $400 extra for a Circle D. This is the converter I'm looking at