I had a "viper spec" LT1 t56 and decided to run it instead of the t5. I needed to convert the t56 to an ls1 style which involved replacing the input shaft and transmissions front cover/bearing retainer... Tremmic calls it a "mid plate" There is no center register in the t56 bellhousing so to check runout, you have to bolt the mid plate to the bell. And check it on the bearing race.