Trying to decode an engine.

[rs74]

I bought what I believe is a 283 out of a 66 El Camino some time ago. I went out today and got the numbers off the front passenger pad on the block. They read "F0820DE". I would like to see what year this is. I found a site and if I used the letters correctly in decoding then it says it could be either a 1958 or 1962 283 or it could be a 1968 307. I used the DE to determine this. I am sure that I don't have this right.

Could someone tell me what I have and explain to me how to decode these numbers. Thanks