[mockingbird812]

Kind of hard to boil the market down to just a couple of variables. Might consider these too (does not necessarily only apply to a Yenko, IMO):

1. Provenance
2. Documentation (none, a bit, a lot) dealership docs, factory docs, owners docs (i.e vintage photos, log books, trophies, etc.)
3. Ownership history
4. Quality of restoration work
Pre & during resto photos are a plus
5. Parts: Original vs. NOS (factory ass'bly line vs. vintage over the counter vs. GM still makes the part) vs. repop (the term, NOS, is very much misused).
6. Original sheet metal
7. Delivering dealership is important to some (may or may not bring more $ though)
8. Race history
9. Transmission/rear gears (i.e. M22 vs. M20 or manual vs. auto; factory 4.56 gears vs 3.73)
10. Original survivor is very popular and in many cases brings higher $ than a great resto.
11. Unusual factory or dealer installed (documented) options
12. Over all rarity (considering desirabilty of course)