OK so my car is stored far away from where I live. Last week I went to take off the front drums, but I didn't have a socket the size of the spindle nut, and it is torqued on there pretty good. I am going to stop by harbor freight.
What size is the spindle nut on the front of my 68 drum spindles?

Never used a socket, channel lock pliers or vise grips always work for me. Vise grips are easier, just lock and roll. Be sure to remove the cotter pin.

What if the last guy used an impact gun to put them on? Will those methods work?

I don't think anyone would use an impact for this. You would crush your bearings. The spindle nut is usually not "tight". Tighten them up snug and then back them off so your cotter pin will go through.

There is a cotter pin in there that may be hidden by the grease, remove it first.