Depending on your car's capabilities and your current vs. future plans for the car, you might want to consider VW-Chevy adapters like RangerBEH mentioned. I found it was pretty hard to find nice looking wheels with a VW bolt pattern, so I went with adapters since I didn't want to invest (at the moment) the serious $$$ required to convert my brakes to disk with a Chevy bolt pattern. This would allow you to retain your Chevy-bolt-pattern wheels for use in the future if/when you upgrade.
I've also been told that the adapters don't handle power as well as proper hub-mounted studs, so if you're building a fast car with a big engine, you might not want to consider adapters. However, if you're building something to go "slow and low" like I am, they're a cost-effective option. And it leaves you more up-front $$$ for cool wheel/tires!
Off tangent, back to topic: if you're looking at doing the brake conversion now, go with a Chevy bolt pattern. As Peter says, it opens up a huge range of wheel options!