Good morning Mike,
If you only want to drive the alternator then the following belts
should work fine:
1) 4 rib belts from NAPA:
 270 mm  -   NBH 25040270
 274 mm  -   NBH 25040274  (just about the longest you can use)

2) 5 rib belts
 273 mm  -   Dayco  273k5
 275 mm  -   Dayco  275k5  (the longest you can use)


If you want to remove the ps pump and want to know which belt will work to turn the alternator....
You can get rid of the PS pump and use a shorter belt.  There is a 4-rib 27" belt that works well.  At the auto parts store, the belts are designated by number of ribs and length in inches, and each manufacturer has a different code like 270K4 or 5040270.
It has one less rib than the stock belt, but it is also turning one less accessory so it works well.