David,
Oh, probably so, perhaps as early as the '63 Riv. I forgot all about the Riviera.
Usually Oldsmobile was the experimental divison, and the Toronado didn't come out until '66, which had the thm 375, a turbo 400 for front drive.
I only know the new trans didn't go into any Chevy's, Pontiacs, or Buicks until '65 when the big block 396, 427, 421 super duty, and the Buick 430 Wildcat came out.
Cadillac may have also used it before '65 on the 390. Maybe the rear drive Olds 425 V8 also.