Yep, my experience has been it depends what crowd you run with, some will want nothing to do with a NOM car and turn and walk away, for others it will be a bonus and have no affect at all - No grey area here so either way it will appeal to 50% of the market come time to sell.

 

From just looking at the cars in my area. I think its more of a percentage of the value to the uniqueness of the car. A base model coupe numbers matching average condition is going for 10-20% more than nom. The base convertibles are 20-40% more. Big blocks are double or more. Its on the buyer too. Motivated sellers may keep the prices reasonable and people wanting big bucks that arent in a rush will sit on them. Look at the makes me want to cry thread. Alot of those cars are worthless but the owner thinks they're priceless.

Your question is difficult to quantify. I would say 2-7 grand if the interior is in decent shape but the car has some small issues, a driver. Collector grade all originals would be astronomically different.

Mine was listed at $21k, owner was desperate to unload before winter, he bought it to flip anyway. He relisted at 19k firm. It had a 72 LT1 350 in it.
It has minor issues that ive been fixing, mostly stuff that is solvable by reading and asking questions here and replacing worn out parts.

The drivers condition I bought it in appraised for $23k and I have ins for $20k. I will be upping the insurance this summer to the appraised price.

Similar cars are listed for 24 to 27 with matching numbers.

In the end I would have preferred numbers matching just because, its the ocd in me. But I really dont mind. I will eventually put in an era correct 327, ocd will win someday.

 

NOM more seriously erodes price the more 'desireable' (rare) the car is.
It can reach as much as 50% reduction on specialty cars.

 

This is a good point. A 427/435 horse car with a 350 in it should be reduced significantly. I was thinking more along my lines in my post. 327 original with a 350.

 

Since we're assuming the high prices paid for L88's, LS6's, or other desirable, low production units are due to the rarity of an original, I'd have to agree. However I also put value on condition. I see the base value being determined more by condition. Good paint, no rust, good mechanicals don't come cheap. Cheaper cars needing either paint or rust repairs are rarely a bargain over one which needs neither. From this base the price rises depending on desirability and rareness. The fixed percentage doesn't necessarily apply if we're looking at a numbers car with little original equipment, in need of rust repair and paint vs a non original in excellent condition. When evaluating a potential purchase, I ask if there are others in the same condition, same configuration, at a better price. I'm assuming we're talking about a car to be driven, not bought only for collector value. Bottom line IMO is whether there are others which fit the list of attributes I'm looking for at a lower price. I've never compromised what I want for a lower price, I'm not buying a commuter.

 

I've noted that some people that don't have matching numbers say it doesn't matter but people that have matching numbers car care a great deal about them. I wounder if NOM folks would care if they had a matching number car?

 

I don't think anybody can reasonably say matching numbers don't matter. Obviously they do to some people. So far as NOM owners wishing they had matching numbers, I doubt many do, else they would have bought matching numbers. I'd say NOM owners probably don't turn away from matching numbers, more likely it's not an attribute they will pay extra for. I do think some buy matching numbers to be part of the group who feel what they own is better than the others, human nature. No doubt the significance of matching numbers may be downplayed by those who don't own one, played up as much as possible by those who do. My take as stated earlier is a solid Corvette, no rust, good paint, good mechanicals doesn't come cheap. I use this as a base price. Price goes up from there depending on demand for what ever attributes, matching numbers, performance engine, rarity, or any combination of these attributes. So long as some people are willing to pay a premium for matching numbers, then they certainly DO matter. To what degree seems to vary.

 

I'm pretty sure the 350 I'm about to pull out of my Vette to swap for a 383 I'm building in another block is the original engine, but I haven't actually checked the numbers. The t10 manual box that I've already pulled for a tremec was/is. I plan to sell both to recoup some of my costs...

I don't plan to ever sell the car. As I said, matching numbers matters not one bit to me. They certainly matter to some people though.

 

How about a NOM 427/435? I would expect this also would reduce value significantly since it was a rare car to start with. It has lost its collector value, buyers most likely looking for a driver. Any premium paid would be for the performance of the 427/435, not its rarity. If the NOM were 'correct' it could do well in NCRS judging if that's important to a buyer. I have to wonder how many 427/435 Corvettes are truly original...