There are alot of good converter compamy's out there today that work good as was stated. That said I have only ever used two different one which are Dynamic and Turbo Action and both work great for me. My son and I both run the 9.5 Dynamic street/strip converters that flashes about 4200. They drive very good on the street and work good at the track.
I used a 10" Turbo Action in my old 383 Dart and it also drove and raced real good. I was actually going to go with Turbo Action for my 63 but then after I noticed the Dynamic was a tad cheaper and Dynamic's shop is only 1 hr from my house I decided to give Dynamic a try since I heard alot of good about them. And Turbo Action is in Florida which is about 28 hrs from my house. I have been very happy with both brands as they have woked just as I asked. Turbo Action has been doing Mopar converters for a long time and Mr Luppo of Dynamic has also been doing converters for a long time.
There is probably around 10 very good converter company's out there. You have to decide which you feel has the best positives about them and then give that company a call. Good luck , Ron