1973 340 block or engine

I am in need of an early production run and late production run for 73 Duster 340. The last 8 digits of the vin will be on the pan rail. Hate to be so cryptic but too many people have told me "yea I got that" and its nowhere close. Home base is VA, but travel extensively. Thank you, Pete

I cannot figure out how being "cryptic" will enhance the likelihood you'll find what you need.