Pulley alignment on these cars can very quickly become nightmarish, especially if you have any non-factory original parts anywhere in the system (such as that alternator you're running). For model year 1969 for example, the Pontiac factory parts book lists at least 4 DIFFERENT water pump pulleys for A-body cars (LeMans, GTO, Tempest, GP) -- all with different offsets.
There are really only a few approaches to getting the alignment right:
1) Make sure that EVERYTHING on the front of engine (all accessories, brackets, balancer, and pulleys) are all factory parts from the same year, model, and option package (and event this can be a challenge for some years and models due to mid-year factory changes such as happened in 1969).
2) Get (or make) an accurate alignment tool and then fabricate specific custom spacers to adjust the mounting "depth" of each individual component until you get everything in alignment.
3) Ditch everything and buy a turn key custom serpentine belt system that includes "everything".
I have everything but the 9799128 water pump pulley.Is it made in the aftermarket ? I ordered #9799127 from The Parts Place, hoping it will work. They said this was correct for a air car They didn't show a pulley for non aIr ?
My car was originally a non air car, it has vintage air now .Is there a difference in the waterpump or crank pulley ?
The least problematic of pulleys that need to be changed out is the chunky chromed alternator pulley. Seeing more and more alternators sold with a pulley for a 3/8" belt instead of the 7/16" belt that is correct for our Pontiac's. It will work but sits very high in the pulley and besides looking funky, the belt rides slightly out of the grooves and is more prone to squealing. The chrome finish also adds to the possibility of squealing.