VIN is not a predictor of when a car was built only scheduled to be. As Barry mentioned there could be a lot of vin numbers in between that were not built in the sequence they were assigned. It would be at best guesstimates.
If the block is original and was cast 6-12-1970 and its assembly date was 6-30-1970 then the car build would come after and would be a July build since the new model year came in Aug 1. Than again it could be July 30 1969 and that would open a up a different can o worms.
The only way to find out is if you post your VIN...then other people with close VIN numbers can let you know what month theirs were built in. With enough info, you can narrow it down.
I'm talking build "month" NOT the day it was built.