What all could i do to make my 77 chevy 350 c20 faster?

I'm not sure what kind of transmission i have but its automatic. I also want to know if i have both rear wheels spinning or just one. If it is just one how would i make both spin? I was thinking changing the gear ratio and puttin in a manual transmission. That should be about all i need to make it powerful and fast. I dont know what size axle i have on the rear end all i know is it's 3/4 ton. 5 lug. Any and all suggestions appreciated.