HELP HELP where are the moter numbers

Where do I find the numbers on the block and how do I tell if it is a numbers matching car. 1970 Challenger R/T 440. The original owner died a couple years ago, so I can't ask questions. I have the original bill of sale, window sticker, fender tag, owner manual, etc. Also where do I find the build sheet(not under rear seat) Mike typhoon@cascadeaccess.com