Your 67 wouldn’t have had a 307 as the stock motor. The 307 came out in 68. You need to figure out what you got.
Here’s a couple links to some info on small blocks and pics and info to determine what your engine is.
Here’s a sb wiki.
https://en.m.wikipedia.org/wiki/Chev...l-block_engine
Here’s the place to look for the pics. Look in casting locations.
https://www.mortec.com/
Once you know what you got then you can decide on a motor plan.