Easiest way is always just transfer the coins to the new wallet with new addresses.
Why hassle with old private keys?
The only reason I can come up with is that you have some vanity addresses you would like to reuse.
Of course don't delete the old wallet, just put it somewhere safe.
It is a vanity address which I would be using but I guess I can always generate another with the same prefix thanks for the help.
Well, I did not say it was impossible, there still might be way to convert.
But if you have a short prefix it would not cost too much effort to generate a new one.