Peter, welcome to the board. I'll take a stab at your first question. I believe it's been discussed in the past, but I'll give you my personal opinion which may differ from others. To me, I rebody involves removing the vin tag and trim tag from a rare car (say a yenko) and re-attaching them to a new body. In this case the "hidden VINs" do not match the vin tag. To me, it's no longer a Yenko.
Now, if the same process involves saving the firewall/cowl area of the Yenko and using the "good body" for the remainder of the car, I'm OK with that approach. To me, the "soul" of the car is the firewall/cowl area w/the hidden VINs.
I believe the collector car market in pretty much in line with this thinking as I know a certain ZL-1 originally sold in the N.W. that is exactly as you describe. A set of tags on another body. When this car changes hands from time to time, it seems to sell at a 50% or so discount from a "real" ZL-1. Nonetheless it still holds significant value over a run of the mill '69 Camaro.
Here's a link to the ZL-1's
http://www.barrettjackson.com/auctio....asp?id=158745 http://www.barrettjackson.com/auctio....asp?id=168273 $64,000 versus $134,000.
[Edited by COPO (12-24-2001 at 02:52 PM).]