A torque converter is a key component of a system called a race car. The stall speed and size of the one best for your application depends on a lot of stuff beyond where you want to shift, keeping in mind that might not be where your engine wants you to shift it.
Start by reading the article in the link below (ignore the Chevy stuff).
link
: http://www.superchevy.com/how-to/transmission/sucp-0207-torque-converter-selection/
Now go to this link to PA Automatic and download the form at the Order Form button. With all of that info at hand, call any company that makes racing converters and chat with them. For between $600 and $1200 you will be off and running.
link
: http://www.performanceautomatic.com/transmission_guide/
My 68 Mustang is being converted from street strip to a full time racer. The current converter stalls at 3500 with a 6000 shift point and the new one will be around 4400.
Dale