Actually, the Toronado and Riviera did not use a transverse mounted engine, it was in the normal, water pump at front, cylinders on the side configuration like any other GM car of the time. It was front wheel drive, but the connection to the torque convertor was at the rear of the engine by the firewall. Here's a link to a pic - hopefully it works:
http://i153.photobucket.com …5/TORONADO/Picture028.jpg
Right you are about the '60's FWD Oldsmobile Tornado not having a transverse engine...brain fade on my part I guess. 
The '60's Buick Riviera did not use a transverse engine as you said...but in the case of the '60's Rivera...the Riv was Rear Wheel Drive, unlike it's Olds sibling which was FWD. Also back in those days...Oldsmobile used Oldsmobile engines...Buick used Buick engines.
I liked the old days when each division developed their own particular engines. Some might say I'm stuck in the past...I do recall the past with some warmth.










