X2 on PTC. We don't use anyone else for Custom converters. Like anything else, I have them build what I want for each individual combination. I don't rely much on the manufacturer's decision. I am mostly going by Engine dyno sheets and/ or just my own personal experience, not Chassis dynos as we don't really use them. However If those are your peaks, I wouldn't go with a 3,800 rpm converter either. A converter in your car will make all the difference in the world provided it still hooks after you put it in, also depending on how you plan on using it. If you set it up for optimum performance at the track but just cruise to the local Gas N' Sip then I would go right to 5,600-5,700. With more focus on street driving, I would back it off a bit, probably 1,000 rpm, and I would put that in a 9". Those are just rpm numbers mind to help get the engine in its power range where it needs to be to accelerate the car, but HOW it's built is just as important. There is a bit more to it, but I am sure you get the idea. Hope this helps.
