OK, so now that gas is more expensive than gold, what type of gas do I use in my 1950's and 1960's cars?

I have some early 1950's trucks with straight 6 motors, a 1964 Plymouth Barracuda, and a 1967 Olds Cutl. What type of gasoline do I use in these vehicles? Also, I have been researching and some say don't use the modern oils in older vehicles. Then, some say it is OK. I am soooooooo confused.