as an FYI
Circle D has been the "go to" option but I did read somewhere that TCI now has a bolt together style converter (similar to Neal Chance) that is offered in various stall speeds as well
The issue with an aftermarket stall is getting it to work well with the trans shift parameters. Several of the '11-'14 V6 guys have gone to a Circle D, and played hell trying to get it dialed in. It's was especially true with the 13-14 cars due to the select shift/sport mode. Hopefully someone is working on it and our 6R80 parameters aren't a PITA due to the Sport mode/paddle shifters like the 13-14's. A mild stall with the some of the turbo upgrades that are soon to be available would be a monster combo.