I had a 78 model king cab. It had about 100k when I bought and about 190k when I sold it. I had it about 4 years and beat on it about like you would expect from an 18 y.o. It needed a new carb that I couldn't find for under $500 at the time. I found my 71 Chevy for $600 when my carb laid down so guess which one I bought.
If I went easy on the pedal, I could get 30mpg with an automatic.