Choosing a converter isn't all sizes and stall speeds. You have to get the physical attributes right, too. For example, some engine mid-mounts can have an effect upon the engagement of the converter into the transmission input. In other cases, the bolt pattern on the converter is important, particularly when the time comes to match it to your flexplate. In Chevy applications, there are normally two different torque converter bolt patterns used. What if you don't know which is which? Simple. Some converter manufacturers offer double-drilled converters.