Heads, and other question..

I have a 302 in my mustang and I know it was a crate motor but I don't know I don't know all of its specs, the last time I had my manifold off I looked under one of the heads and it had E080 stamped on it I think that means it has 1980 heads is that right and if it is right how much hp do you think I will gain from switching to E7 heads I heard that ford made those heads much better I may be able to get a set of E7 heads for $30 and I don't know if it is worth swapping them out. I also had a question about my speedo cable gear I put 3:55's in my car but I didn't change the speedo gear I know that my trans has a yellow 7 tooth gear on it and it it s world class T-5 does anyone know how many teeth my speedo gear needs to have?

In the book I have it says nothing about E080 heads for 79-93. I'll have to do some more looking.