You posted this a while ago so you may already know this, but death certificates are a good source of information, and most states started keeping them around the first decade of the 20th century. You can send away for your grandfather's death certificate from the state he died in, and if it's complete it will tell you his parents' names & birthplaces. If he died young his parents may have also lived into the 20th century and you could get their birth certificates. My
Tock line came from Lincolnshire
England, and there were many Tocks there in the 19th century, so it may turn out that they come from there.