The pulleys don't line up to be able to use one belt; the p/steering has a 3-rib belt and the crank/alt uses a 5 rib belt. The crank pulley has different sections for each belt, so unless you find something that fits and lines up with all the pulleys... can't be done.
I got rid of the AC and my local parts store (Checker) had a listing for cars without AC. It fits, don't have the part# handy right now. That rockauto number looks close, the last three numbers are the belt length in centimeters, so you might have to add or subtract a few to get the right fit. They go by increments of 5 too; like 395, 400, 405...
Babble On
Dan