What if you had a 69 yenko with a non original motor, and a 69 camaro, all original 6 cyl with paper work.I would pay more for the yenko.I guess it all depends on the car.If you have paper work on an original car,I think a CE replacement engine would be fine but wouldn't be worth as much as an original,and would be worth more then a car with a non matching engine.I am glad I bought my car 20 years ago.It would be hard to know your getting an original car today, with repoduction protecto plates,window stickers,broadcast sheets, heck even repo 69 camaro convertible bodys.