1972 Plymouth scamp 318

Ok I just bought myself a 1972 Plymouth samp with a small block 318. And the fuel pump just blew, I've fixed it, but now there is gas in my oil. And I know I need to change my oil before it destroys my bearings. My problem is the original owners manual that came with the car, does not tell what type of oil to use. So my question, and as sad as this sounds, what type of oil does my car use?