It's highly unlikely a 1987 Cadillac transmission will work in a 1992 DeVille. While both are Cadillacs, there were significant changes in transmissions and drivetrains between those model years. The bolt patterns, computer interfaces, and even the physical size and internal components are likely different enough to prevent a direct swap. You'd run into numerous compatibility issues.
You'd need to find a transmission specifically designed for the 1992 DeVille's engine and chassis.
