Tech, dont forget that the 307 is a "big main" 283 block.....that suggests that you could put a Z/28 crank in it and make a 283 that was a late model one.

There needs to be a 262/265/283/305/307 page since these questions seem to pop up every 12th post.....with small variations.

Tech, your tip is ABSOLUTELY right.....put the old engine in a plastic bag and save it. Darn few folks can tell a 350/383/400 from an original smaller engine, especially when it is installed n a car. I remember too much the pains of rope seals, etc. Modern stuff is much better.

mike in tucson