I wanna say you can use one of the stock length ones, but I don't remember which one I used when I had my smog and PS bypassed.
Also, general rule: find a longer old crappy belt and cut it, then use it on the pulleys to find the length you need. Then, you can usually get a size in either direction at the parts store, see which works, and return the two you didn't use.
Put a NAPA 25-9355 around the crank and water pump. It's exactly the right length to fit with out a tensioner in that loop. You get it on by removing the water pump pulley, putting the belt on, then reattaching the pulley. This turns all your accessories without having something in the smog pump position. That leaves the configuration as Crank:Alternatorower Steering Pump, Crank:Water Pump, and Crank:AC