200-4R swap - SUCCESS!!!
As reported previously, one of our first goals for my recently acquired '67 Lemans/GTO-clone project car was to swap the original ST300 2-speed transmission for an aod.
Between this forum and information pulled from SA Design's How To Restore Your GTO, we felt fairly confident we could make this happen. A local boneyard supplied the trans, sourced from a 1989 Cadillac. An Aamco Transmission shop quoted a very reasonable price to do the work - so my husband chose to turn it over to them rather than tackle it himself.
We actually got lucky with the Aamco shop in particular, because these guys are really into vintage muscle cars, including one tech who is a big GTO fan. They checked out the trans, found it to be in good shape, bolted it right in with no modifications necessary to the rear mount or driveshaft. Even the trans' dipstick tube fit right into place behind my car's later-model 400.
Summit Racing-supplied torque converter lock-up kit and kick-down cable kit completed the installation and we drove it home today. Works great. Little bit of an adjustment to the kick-down cable is in order, but all in all we're good to go. Trans cost $250, and Aamco charged $850 for the entire job. Factoring in cost of the Summit components, and considering improved drivability and fuel economy, it would seem to be a very good investment.