Model 99 cartridge convertion ?

[Hallbilly]

Model 99 questions. Never actually seen one but they do look nice and appear to be a robust practical rifle, I'm sort of getting interested.
Someone local is selling a model 99 in 3030 with a shot out barrel and there doesn't seem to be much interest in it.
I'm not afraid of re-barrelling but while spending time and money on it how practical would it be to covert to 243 or 308.
Also see some are advertised as being breakdown, were they all breakdown or were there specific builds ?
(Post edit. Sorry, Breakdown...Takedown : Tomato... Tomaato. Blame it on my British Colonial up-dragging).