For the money you cant beat T/S (transmission specialties) spragless racing converterss, they list for around $900 which is about the going rate for a "good" name brand converter.
Dont skimp here - buy a good one and be done with it.
They also offer one free tweak within 90 days of purchase.
Heres a link to their site.
http://transmission-specialties.com/?cPath=23
Goodluck, Cp