You can buy the bolt-in Comp. Engineering ones for about $ 100. If you have a convertible, you will have to notch out the floor brace under your floor, or notch out the frame connectors to fit around the brace.

Check out High Performance Pontiac magazine 2004 issues (I think it was November). Or search the internet, and you can find the article online. They took a pair of C.E. connectors and notched them to fit on a convert. Not a very difficult process, but you (or a friend) have to be able to cut and weld.

The other connectors on the market are extremely expensive, and don't look very strong to me.