Foary

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. It's all stock, no modifications. 1. Which diameter do I need for mine? Is the 258mm stock size? 2. Which stall should I go with? 3. Do I need a billet flex plate from Circle D? My engine is 5.3L 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: https://www.circledspecialties.com/collections/converters/products/8l90-hp-series-258mm The truck is my daily, I just want to fix the torque shudder issue from factory.