Bernie, it sounds like someone put a single groove water pump pulley on after installing a new water pump. The p/s pump didn't line up, so they improvised and ran the p/s belt off the crank pulley.
Check to see whether you have an 8-bolt or 11-bolt water pump. Someone may have installed a 1968-earlier timing cover at some point.
If you have the 1969-up 11-bolt water pump and timing cover, Pontiac changed their water pump design in 1969. They had a short snout version, used early in the production run, then they changed over to a longer snout version, which became the norm until the end of the Pontiac V8 run. Someone may have realized that after switching water pumps that the p/s pulley did not line up.
If you ever need a p/s belt, you definitely won't find an application in any catalog. I would suggest you look at the current belt and write down any part numbers you find (look for the 13xxx or 15xxx number, the xxx will determine the length). You never know if someday you'll throw the belt while on the road, and a parts store will only know how to look up the application, which of course won't work for your setup.
As for the operation of the p/s pump, you're fine the way it is, but if you could, I would change it. Pontiac ran both belts (alt and p/s) around the water pump pulley as a backup. If the alternator belt breaks, you'd still be turning the water pump and able to get to a gas station. If you broke the p/s belt, the alternator belt would still be turning the water pump. So the way your setup is now, if the alternator belt breaks, you'll have to shut the car down because the water pump won't be turning.
Some info I found while searching...
In ’69 Pontiac changed to an 11-bolt water pump but the early ’69 was different from late ’69-on. Many early ’69 Firebirds and GTO's used a pump that measured 4” long (casting# 9796351) and the pulley was 2-1/4” in height. From late ’69 to ’79 only one pump style was used, it measured 4-1/2” long and there are at least two different casting numbers used: 482138 and 488296. The matching pulley should measure 2-5/8” in height. Always use the correct diameter and style crank pulley to match the water pump pulley and also use the same series timing chain cover and balancer to properly line up your timing marks.
If you need to order a water pump the Federal Mogul part numbers are: ‘64-’68 is FP1388N, early ’69 is FP1409N and late ’69-on is FP1423.
