If you are going to attempt a clone do not do it with the purpose of misleading a buyer at the time of sale!!! It is illegal to change VIN #'s! If you are going to attempt to clone do it completely. The dash can be a sure giveaway if it has not been changed. The SS dash on the 70 -72 are completely different from the other Chevelles. These dashes are gauges, where as the others are long speedometers with idiot lights. Dashes on the 70- 71 and 72 have the seat belt warning light. New interior wiring harness, forward lighting harness (or modify yours) suspension (sway bar, boxed control arms, etc), 12-bolt rear, front disc brakes, emblems on doors, chrome, bumper pad, grill, paint/stripes, all these items will need to be addressed. If you do it right you probably could purchase a real SS with the expense. Also the functioning cowl hood is way cool. There are more items. Under the hood, the frame-side motor mounts are different for small block or solid block-side motor mounts could be used with the Big Block. The passenger side front brake line is also different, crossing over the frame closer to the firewall than a smallblock car. This is for extra clearance from the exhaust manifold. The SS always had a 12-bolt rear end from the factory, and there are a few extra frame support brackets for the rear suspension pickup points, but these, as well as the brake line are often overlooked. So really its the hood, dash, emblems, stripes, rear end, and engine that make up the biggest items. I could go on longer but it has all been done already by Daniel Carr! Here is a link to the best SS cloning page on the web.
http://www.chevelles.com/shop/ss_ident.html