I just did a 4L80E conversion. I was running a TH400 with a loose converter. The lock-up converter with the OD tranny is awesome. At 65 mph running 3.23 gears my rpms dropped from 3000 to 2000. That impressed me. It's pricey though, and you might be ok with a 200R4 but I just knew I would be one of those guys that killed the 200 in a short time so I went with the heavy duty route.