I have measured the ISO speed of Delta 3200 to be 800. My methods are not highly rigorous, and I can't disagree with those that say it is 1000.(posted 9076 days ago)I get this speed with T-Max developer, 1+4, 24 deg C, 9.5 mins. If I wanted to push it by 2/3 stop, I don't know how much extra development it would need, but I might try 12 mins.
I haven't experimented much pushing with this film, because I don't need it and I don't like the results.