A good shift kit will help that snappier thing. I use a 2000 ish converter and I am very happy with it for street driving and cruising. Someone had a Hughes converter for sale for $100 recently.
A custom built converter, like the ones that Jim Weise has built for him. I think he mentioned he had a 9.5" converter that he sold to guys with bigger cars like Electras. You want a converter that will complement the power range of the engine. You want it to feel stock until you jump on it. For that you have to pay more. https://www.v8buick.com/index.php?threads/tsp-9-5-street-strip-converters-lifetime-warrantee.147066/ BTW, you do realize you are posting an automatic transmission question in the Manual Transmission Forum? Kind of counter productive.
I would simply buy a generic 2500 stall, it’s not rocket science and there is no need for a custom converter for a mild 455. We know how much torque it makes and that’s really the deciding factor to raising or lowering the actual “flash” stall rpm vs the “stall rating”. More torque raises the RPM less lowers it. A common 2000 stall will likely flash to 2500 on launch behind a 455. if it’s a high $ setup with custom needs then yes a high $ custom converter is key.
