I have one 1991 LS400 donor with bad transmission and I have a 1992 SC400 good transmission. They are complete bolt on swap. All the plugs are the same. 1992-1994 transmission from SC400 is same as 1990 to 1994 is the same. The only different is the gear ratio. Due to the LS400 headers and SC400 header difference, it is best to swap out the transmission pan also. The dipstick has different configuration. Just would like to share with you guys have difficulty finding SC400 transmission. Generally speaking the LS400 transmission is alot cheaper than SC transmission.