I bought F-body calipers and brackets off eBay, rotors locally,pads from an online store, and the collars form McMaster-Carr. In total I paid ~$150 for everything IIRC.
That said, I knew exactly what I needed and I took my time finding used parts cheap and in great shape. If you don't want to go through all the extra hassle, just get them from the W Body Store or ZZP.