"What is the WS6 Performance Package?"
In 1978, Pontiac came out with the WS6 Performance Package as an upgrade to the suspension on the Trans Am in 1978 (Named the "Trans Am Special Performance Package") and on the Formulas and Trans Ams in 1979 and later (Named the "Special Performance Package"). The package consisted of a larger diameter sway bar, tighter steering box gear ratio, GR70-15 raised white letter GoodYear Polysteel Radials, and also the 15x8 inch snowflake rims which the total package was between $251 and $324 upgrade cost depending if you also went with the W72 Performance Package as well. In 1978, the rear brakes were still the drum brakes with the WS6 Performance Package. The rear disc brakes did not come out until 1979. One of the main additions with the WS6 Performance Package was the 15x8 Snowflake rims which really gave the car a wider stance. The sway bars also were the larger diameter which the rear is shown below.
|Non-WS6 Package Sway Bars Front/Rear
1.250" / 0.625"
|WS6 Package Sway Bars Front/Rear
1.250" / 0.750"
Now in 1979, they added the rear disc brakes to the WS6 Performance Package. So, it included everything listed above, but now had 4-Wheel Disc Brakes all the way around. But there are a few confusing items for 1979 in determining if your car is equipped with the WS6 Handling Package. Just because the car has rear disc brakes, does not mean that you automatically have the WS6 Package. In 1979, you could order just the rear disc brakes on your car using the J65 RPO code and not have the WS6 package. The second confusing issue was that there was also a WS7 Performance Package in 1979 as well. Because of the popularity of the rear disc brakes across the Pontiac car line, they actually ran out of disc brake rear ends. Because of the overwhelming response for the WS6 package, but lack of the rear disc brake availability, they came out with the WS7 Performance Package which was the same as the WS6 package in 1978 that had rear drum brakes. So, having disc brakes or drum brakes in the rear in 1979, doesn't mean your car did have or didn't have the Performance Package.
Another item that has also come up in discussion is the front springs. Some say that the front springs were different in 1978 between WS6 equipped cars and non-WS6 equipped cars. Here are two build sheets shown below. Both are from 1978 with one Trans Am having the WS6 Performance Package, and the other came without. If you look at the GM codes from the front springs, they are KW and KV for both cars.. with or without the WS6 Performance Package.
|With WS6||Without WS6|
How to know for sure......
All of what is listed above is what came stock in 1978 and later. When helping to determine if the car you are looking at did originally come with the WS6 or WS7 Performance Package, the two best options you have is the original build sheet, or the PHS Documentation. We are talking almost 30 years later and some modifications to the car could have been done in the past. It is fairly easy to purchase a set of 15x8 snowflake rims and put them on your car. It is also common to add rear disc brakes to a car and also purchase the larger diameter sway bars as well. So, your best bet for documenting the car would be the build sheet , or the PHS Documents.