I had a friend call me wanting to sell his 1968 camaro it is a 6 cylinder vin but has had a 350 installed engine bad car has no rust all pans great trunk has original paint with no rust car is butternut yellow and has been stored 20 years. int. is good. what is it worth ?

I wanted to know how much less car is worth because VIN. number shows 3 for 6 cyl.

I wanted to know how much less car is worth because VIN. number shows 3 for 6 cyl.
...swapping from a 6 to an 8 cylinder, ...most likely isn't going to have any adverse affect on the price of the car.

Some people would see the L6 VIN as a bit of a deterrent, but typically doesn't have a huge effect on pricing. Probably a grand or two, if anything.