Not so Tim, there are a few of us who value the side oiler above all other engines choices for a 427 Cobra. In many cases the sale or purchase of a Cobra can be directly tied to the type of engine. I know of several cases where a sale was NOT made until verification of the engine's side oiler status. Center oilers need not apply, alloy engines won't cut it. Extreme KC engines just don't have the soul.
Will the engine (427 side oiler) appreciate over time? I wouldn't bank on it! But then I wouldn't bank on ANY replica to appreciate over time. Will it hold it's value? Compared to what? A new BMW, Caddy or whatever? Yeah, it most likely will do better, good chance it will depreciate over time though. DON'T buy a replica for ANY kind of 'investment' purposes!
So how about a 'date coded' 1966 side oiler compared to a 'service block', say 1968 side oiler? The '66 has a better pedigree, a better 'wow' factor, it will certainly garner more respect from me than a service block. And thats true for a number of people not swept up in the 'modern is better' demographics currently in vogue with most replica owners. Some of us are still into 'old school', which is fundamentally what the Cobra is all about in the first place!
Some where along the line many owners have lost the appreciation for that aspect of the car, to many...
Peter, you do something like admire a correct date coded 1966 side oiler because YOU like it. NOT for braggin' rights, not for resale, not to impess somebody (but I AM impressed

) but for the spirit, for the soul, for the history it represents. Drive it proudly (and try not to smirk when the guy parked next to you pops the hood to show of his all alloy 'trick' modern motor, OK?).
Think about it, the really GOOD quality replicas generally have the really GOOD engines, good being a relative term of course. A side oiler in an ERA is pretty common, great car, excellent motor choice, well done! How many side oilers would you find in a Backdraft? An FFR? Any number of other replicas? Not so much. Older Hi Tech? Contemporary? Early Kirkham? All terrific replicas and your likely to find a side oiler under the hood. Built during a time when there was more appreciation for old school than there appears to be today.