Edgar, there is no more PB, 7625, or 4756. I would first go to the powder company web sites to see what works in the 16ga.
http://www.hodgdon.com/ or
http://www.hodgdon.com/ are two of the biggest. BPI's SG16 looks like the shortest wad they have and it's what you want for 2 1/2. Here's their web site - call and talk to them.
http://www.ballisticproducts.com . You guys with reloading questions - we have a forum for that - it's near the bottom of the forum list.