I can't help with the fiberglass hood spring question, but I can with the Dana 60 question.

Yes, all the cars that were sold new with a Dana 60 had "SureGrip". There were two different styles offered and the PowerLock was the strongest, but even it could be worn out. I have a 30 spline PowerLock carrier for 4.10 down gears that I was going to use in my '64 Polara until I found a Torsen Gleason worm drive and used it. This unit is now made by Eaton and does not require special fluid additives to prevent chatter around corners. They are completely transparent in operation and are the best answer today for traction.