I have a 70 Chevelle and have been researching this topic also... So far, I've found that Kore3 and Touring-Classics have good reputations and usually come in costing less than the comparable Baer kits. I've also heard that some supporting vendors (Frank at Prodigy Customs) offer some good prices on Wilwood packages. Perhaps someone else can comment on personal experiences with any of these kits or vendors...
Based on what I've researched, I can tell you that TC's website is easier to navigate and select the right kit for your car. That said, Kore3 has more options to choose from, including the higher-end stuff like Z06 and Z51 brakes. Both offer basic C5 conversion packages for the Chevelle. I've been eyeing a kit from TC which includes a 13"/12" C5 kit with master, brackets, and brake lines for around $1700. Add $165 for a booster and you're still under $2000 for everything. I tried to price a similar kit through Kore3, but got distracted with all the Z51 and Z06 goodies. Too many variables!
Good luck.