Verifying Matching Numbers

I am wondering if anyone out there can help me? I typically purchase old Mopars (no booing please!!!). However, I have decided that I am going to purchase a 1970 Mach 1. I am currently looking at 2 cars...one with a 351C and one with the 428 (non ram air). I know on the Mopars there is a casting# and a stamp that matches the VIN. How do you do this for the 1970 Mach1?? Can someone out there please help?? What exactly would I look for and where on the block? Should there be a stamp that matches the VIN for Mach 1's?? Thanks gents.