To some it is "only" a replica & the motor they use to power it is just that, "only a motor".
To me personally, I feel that these cars are more of a tribute to the legacy & prefer to match the correct motor with the correct car. & with that I also feel it is a persons preference to do as they please but often wonder why someone would spend the extra money on say an ERA & not just go the extra 10 yards to do it correctly. Just my opinion
