GoofyTimL, you will be made welcome down here but I doubt you will be able to rent a 300C, V6 or V8. You never know if a boutique Car rental company might get one but it will cost an arm and a leg.
On the Octane vs RON discussion. I don't know the conversion formula but Chrysler advised me when I raised the "issue" of them recommending 95 RON that it was equivalent to 89 Octane in the US.
Some old threads suggest that a higher than recommended Octane with mess with the MDS so don't do it.
