Not sure if it varied from plant to plant or different from year to year. But on my 66 Chevelle the block has year, plant and the last 6 of the VIN on the engine pad but only the plant and last 6 of the VIN on the trans. This is when they were still hand stamped so not sure if that changed when it went to gang stamping later on. Also, I will add that my car was built at the Fremont California plant and their stampings could be all over the place with mistakes.
http://www.chevelles.com/forums/35-r...k-track-7.html