I see a lot of older Pontiacs with later engines that have had problems getting pulleys and brackets figured out. This is some info that can help.
All of the timing chain covers from 1964 to 1979 will bolt up and interchange with any motor from those years. However, you must use the matching water pump, pulley and crank pulley and brackets to avoid alignment problems with the alternator and/or power steering pump and A/C. All of the water pumps from ‘64-‘68 will interchange. These pumps have eight bolts and measure 3-5/8” long (from base to water pump pulley flange). The casting number for ‘64-‘65 is 9772716 and for ‘66-‘68 it is 4782482. The matching pulleys are 2” in height. From ‘64-‘67 Pontiac used a small diameter (5.25”) six bolt two-piece harmonic damper and from 68-79 a large diameter (6.75”), one piece four bolt damper was used. In ’69 Pontiac changed to an 11-bolt water pump but the early ’69 was different from late ’69-on. Early ’69 engines 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. Always use the correct diameter and style crank pulley to match the water pump pulley. The non-A/C cars used smaller crank pulley and a larger water pump pulley and the A/C cars used a smaller water pump pulley and a larger crank pulley. Also use the same series timing chain cover and balancer to properly line up your timing marks. The same timing chain cover was used for both ‘64 & ‘65 and had just a simple pointer. These were cast with number 9773371. The timing cover used on ’66 and ’67 employed a small timing scale marked -4, 0, and +6 and is otherwise identified as casting # 9783130. The ’68, ’69 and ’70 timing covers look very similar with timing marks of 0-6-12 degrees BTDC and accommodated the large diameter damper. The ’68 timing cover casting number is 9790347 and uses the 8-bolt water pump. The ’69-‘70 timing cover casting number is 9796346 and uses the improved 11-bolt pump. For ’71 and later the timing cover timing tab is marked from 4 degrees after to 12 degrees BTDC and is graduated all the way to 16 degrees BTDC. As compression ratios were lowered to 8:1 and lower there became a need for increased initial advance. Casting number for this cover is 482883. 71 and later crank and water pump pulleys are about 1/4” taller and the accessory brackets are set out to match. The 71 and later heads have an extra bolt hole in the front of the head toward the intake side that the alternator bracket uses. There is not enough meat in older heads to drill and tap the hole so it makes it hard to use the 71 and later brackets if you are using the earlier heads. To use the accessory brackets from the 70 and earlier engines with the 71 and later damper and timing cover and water pump you need the 68-70 crank pulleys and the late 69 and 70 water pump pulleys.
Many of the pulleys have the part number stamped on them.
Some common water pump pulley numbers
67 some P/S & A/C – 9788886
68 P/S & A/C- 9788886
69 P/S no A/C – 9796060 (short snout pump)(2 groove for alt. and P/S.)
69 P/S & A/C – 9796062 (short snout pump) (2 groove for alt. and P/S.)
69-70 P/S no A/C – 9799127 (long snout pump) (2 groove for alt. and P/S.) 8″ diameter
69-70 P/S & A/C – 9799130 (long snout pump) (2 groove for alt. and P/S.) 7 3/16″ diameter
70 P/S & A/C – 9799128 (2 groove for alt. and P/S.) 6 7/16” diameter
71-75 P/S, no A/C – 481039
71-75 P/S & A/C – 481040
Some common crank pulley numbers
68-70 V8 no A/C – 9790846 (2 groove for alt. and P/S.)
68-70 V8 A/C – 9790842 (2 groove for alt. and P/S.)
68-70 A/C – 9790843 (one groove for A/C compressor)
71-75 P/S no A/C – 481037
71-75 P/S & A/C – 481038 (2 groove for alt. and P/S.)
71-75 A/C – 480509 (one groove for A/C compressor)
I scanned pulley application and part numbers from a late 72 parts catalog if you want to know what a number fits. Ron Maurer
Click on image to open/enlarge. They are in downloadable .pdf files below.