Re: dont know what types of walls i have
By '77, plaster had given way to drywall, that's not a guarantee that you have drywall, but it is quite likely that you do. Take the cover plate off of an electrical outlet or switch and look beside the box into the wall cavity. If you see wood lath or an excessively thick wall, then you're likely dealing with plaster. If you only see about 1/2" of wall thickness, then you're dealing with drywall.
I suffer from CDO ... Its like OCD, but in alphabetical order, LIKE IT SHOULD BE!!!