Used car rating scores are low, average and high. Low needs major engine and body work and has high mileage, Average need some work, looks about right for it's age, High needs very little of anything.
With a used classic car how does this rating work? How would a 87 Monte Carlo SS, no t top, with low mileage(35Kmiles), average interior, minor tears and a bit of fading, couple of door dings, hood dings and few paint scratches - no rust, still shines, minor floorpan rust, very good chassis, very good drivetrain but possible exhaust pipe work. It seems to be average but how to figure in low mileage and better than average chassis(for the salty climate - no winters but rain and humidity damage. It's not quite casual show quality but drives well.
The standard used car and book value terms of low average high don't really translate well to a classic or collectable car.
If anything, when dealing with a TRUE classic/collectible it's more common to see a number scale - 1 2 3 4 5 for condition.
Opinions vary, but generally speaking it would go something like this and remember, there is a range, think high to low for a scale:
#5 is absolutely parts only. May have paperwork issues, and, more likely it's completely a mess and unrestorable. Think maybe sat in a field 20 years, may not be a complete vehicle, bent frames, etc.
#4 It may or may not run. It may not even be 100% complete, but on the low end there's something there to work with for an ambitious project, or could be used for parts. Could be an abused and worn out former daily driver, something that has been yard art a few years at the bottom of the scale, up to a servicable usable vehicle where some things on it need redoing to be nice. May have rust, missing paint, multi color panels, ripped torn stained interior. High end of the scale would be a basic daily driver.
#3 is a typical nice survivor car, clean body, presentable paint with nicks and scratches, few dings if any. Could be an amateur restoration, the sort of thing that presents well at a local car show. Interior would be clean and in nice shape but not 100% perfect. Runs/drives and shouldn't have anything in the way of issues other than the average quirk an old car gets (say being cold natured when warming up or something) most of the really nice street driven cars you see would be valued as a number 3.
#2 is the ultra low mileage extremely well preserved survivor. Could also be an extremely well done restoration, professional quality. In the gbody context this car will present literally as if it was new on the dealer lot for what gm quality was in the 80s, which, admittedly had issues at times.
#1 is a concourse quality show car, basically something you don't even drive on the road. Paint is slick as glass, better than anything that ever left the factory. All chrome is better than nos production pieces ever were. Body gaps are better than 2016 cats let alone what was in production tolerances when new. These are ultra high end collector pieces that 100k being dumped into restoring is the norm. If you look anywhere on the car, above or beneath it is clean enough to literally eat off of and then be mad the food left residue on the axle or exhaust pipe before you took it off.
Two things to add/edit/update I left off... for grades 2, 3, and 4 you would have cars that rate as high or low within their bracket with some adjustment to value to account for it.
If looking at a classic value guide of the sort nada publishes, that only has a high avg low scale (and isn't a serious collector car price guide) its high avg low correspond to grades 2, 3, and 4 respectively.
