Does a transmission from 1991 Cadillac sedan deville fit 1982 Monte Carlo?

No, a transmission from a 1991 Cadillac Sedan DeVille will almost certainly not fit a 1982 Monte Carlo. These cars used different transmissions, different engine mounts, and likely different bell housings (the part that connects the transmission to the engine). Even if some superficial measurements seemed similar, the internal components and bolt patterns would be incompatible.