Chevy has produced a 305 cubic inch engine, and a 307 cubic inch engine, but not a 302.
To help you out, I need more information to tell you the correct firing order.
Please let me know the following:
* What year is the engine?
* What model of Chevy vehicle is the engine in?
* Does the engine have a distributor or is it a direct injection engine?
Once you provide this information, I can give you the correct firing order.