The cost of non matching numbers car?

[Jim Ferron]

Seems like nobody like to chime in on these WIW threads...but I'll give you an opinion.

I'm guessing 15-20% on a non-engine [base] specific car which a 67 GTO would be...

Certainly a NON numbers LS-6 would take a bigger, much bigger hit. As would a RAM AIR GTO vs. a 335 hp car. A 383 Roadrunner less [10-15%]...a Hemi Roadrunner more...IMO

[Stefano]

I would agree with Jim's assessment. Sometimes a non original engine car is worth less and sometimes it's worth a lot less. But it is determined on a case by case basis.