What other engines (years and sizes) will bolt into my 1978 chevy el camino that came with a stock 305?

I need to replace my engine and would like to know what my options are, especially years and engines from other vehicles. I know it should fit any sbc, I'd prefer either another 305 or a 350. I would also like to know is they made 4speed automatic transmissions that will bolt to the 305 or 350, because the 3 speed in it really doesn't help me with the current price of gas.