Do these pipes need any prep or coating before installation?

Aluminum is naturally corrosion-resistant, but bare aluminum can oxidize over time. Consider polishing or coating them if you want a finished look. Otherwise they're ready to install straight out of the box.

Are the clamps the right size for my setup?

The clamps are sized for 2.25" diameter piping. If your intercooler ports are a different size, you'll need to source matching clamps separately.

Will these work with my custom turbo manifold?

This is a universal kit with standard 2.25" tubing. Test-fit it against your intake and outlet ports before final assembly — your plumbing layout determines whether you use all eight pieces or customize the circuit to your setup.