What is the correct dwell setting for a 1968 Oldsmobile Toronado with a 455 engine?

I'm pretty sure that all General Motors V8 engines use the same dwell setting. Most likely you have a distributor with the little pull up door and points with the Allen screw adjuster. The setting is 28 - 32 degrees dwell so just set it as close to 30 degrees dwell as you can.