"new" 1969 Barracuda

Nice car, love the 69's and it looks to be in very good shape.

IMO, if you are concerned about originality for value, simply do as 1968Formula says and keep the original parts when upgrading. If you plan on swapping the drivetrain, then all of that could certainly be reversed if desired by a future owner.

However, 318 models generally don't command the same value as factory 340, 383, and 440 models of the same year in the same condition. Potential buyers are often looking to either upgrade /6 & 318 models, and if they are already upgraded without butchering, they can often have more interest from prospective buyers.

Ask yourself this, since you want to upgrade it. If the car already had a 340/360, upgraded suspension and possibly rear-end, would you have passed on the deal?

Go for it.

Grant