302 heads are way smaller than 308 heads. You won't need a burrett to figure that out..... Just put them next to each other.

Also, you don't have to run under the index to qualify.
You just can't dial any slower than the index.

When my friend went to his first event running in stock the car was just off the index.
Ran 12.10 on a 12.00.
Lost first round with the 12.00 dial when it wouldn't run the number.

After a bunch of testing and getting the car sorted out it ended up going 10.97 years later.
First GTO stocker in the 10's.