I now have the stock 3 spd OD transmission in my 55 Crown, She has 1957, 312 with G heads and 57 distributor. 570 Holley SA carb. Did not do overhaul so don’t know internals. But runs good and strong. I would like to upgrade the Butter Box stock 3spd W/OD. With something more durable and have OD if possible. As I am reluctant to lean on it from past experiences with this type transmission from back in my day. I final found a tranny that would take a beating and keep on ticking, but lost to many brain cell to remember what I used. I do remember that the gears inside were thicker and fewer teeth then the stock tranny. So hopefully you all are willing two find something I can upgrade to as I always fear that broken teeth that cursed me long ago but learn fix and replace in my sleep. What would you all suggest I look for, are you are using.