Derick,give Tower Hobbies a try,they sometime offer free shipping on orders over $25.I bought my last 2 kits this way(50 Olds and 57 Ford)and it ends up cheaper than buying from the Hobbytown USA in I.F.
They ship from their warehouse in Reno NV.so it only takes 3 or 4 days to get to ID.
Rich
The Revell 64 Impala has a 327 auto.trans.,and the AMT 68 El Camino has a 396 auto.trans.
I'm sure there are a lot more out there,but these are two that I have.
Not sure,but I think a 307 and 327 have the same block,so,either should work.
Rich