With old film the key is what temperature for how long. Cool/cold and relatively dry are good. Room temperature is OK. Hot attics or out buildings (especially in year round heat) are not so good. Development sooner rather than later is best.
Fairly cool chemistry temps are good -- probably not over 73 degrees. I agree that 20 percent additional time should be helpful on this old film. Also, I would recommend a 2-4 minute water pre-soak to get the (old/dry) emulsion ready for the developer. I just use clean water at about the same temperature as the developer for about 2-4 minutes with light agitation. Be sure to drain all the water out. D76 is a good universal developer or use whatever the manufacturer recommends. A good, long wash to remove all the fixer is suggested -- maybe 50 percent longer than recommended/usual. The negatives will probably have "base fog" due to age. You can probably scan "through" the base fog and hopefully have a useable image. If concerned with all the info and recommendations you can always do a "tail test" of maybe one or two images from the tail of the film at your best guess for all conditions before developing the whole roll. Be sure to get at least one image -- and Mr. Murphy guarantees that you will always cut through the best image and the image you wanted. Good luck and let us know what happens.