exhaust manifolds

I have a 98 Trans am LS1. Putting in street rod. Plan on using org. exhaust manifolds. Problem is I don't have the old cats with the manifold flangs on them. Does anyone sell the flanges so I can get a custom exhaust system made or do I have to find some take offs and cut them off. Also I am going to run a afternmarket temp gauge and electric Red. fan I know frompast post that I will use the pass side rear threaded hole on head for the sender. My question is where do I put the electric fan sensor?? Thanks.

Did you think of going to your local Pontiac dealer for the parts that you need to complete your project? The parts department probably has the parts that you need.

I was told that Pontiac would not just sell the flanges by themselves. They come with the cats. I will go to Pontiac today and ask in person.