Big cars of GM had MW9 in 81. Cutlass started getting them in 1983 with the
H/O only. Buick G had them in 83 as well, I believe. By 1984- nearly everyone had one by then. Frames for 84 G-body Olds were built with the proper rail extensions for mounting the MW9 crossmemember. 83 frames for the
H/O had to be "modified" to do that. 83 Buicks probably had to as well, but I don't know.
Any and all 83-87 G-body
H/O and 442 came with MW9.
I concur with
pagrunt as far as the G-body MW9 emergence.
I am unaware of any 81 or 82 G-body with an MW9 from the factory.
From what I can gather, G-bodies were last in line putting in the OD transmissions.