I did a mild build 428 a couple years ago. Started with a stock 350 converter. Had some spark knock that I could not get rid of. Went with a 3000 TCI and it ran great but it lost all of its torque. On the dyno it showed it was locking up at 3600 rpm's. Thank you TCI! Gave Coan converters all my info. and they suggested a 11" 2800 stall. Just getting on the road with the Coan and I would say it is pulling a lot harder. Third time is a charm, good luck.