Hi All
If your doing it under an EASA licence you will need either an ATPL or
CPL Mutli-Engine IR with ATPL theory.
the above will be the minimum you need from what I can gather from the latest EASA FCL docs.
https://www.easa.europa.eu/system/fi...u/Part-FCL.pdf
The details are on page 826
The list of type ratings
https://www.easa.europa.eu/system/fi..._List_Acft.pdf
The C510 Mustang is on Page 6 listed as a SP HPA.
As the comments above indicate, getting an MCC would be a good idea. Getting a JOC is not essential and a good Type Rating organisation would be able to give you the same benefits of the JOC on the type rating.
Some additional advice would be to get experience with Garmin G1000 on pistons so that when you come to do the type rating on the Mustang you don't have to learn the avionics as well as speed control, descent planning and all the other additional systems.
Hope that give some specific details, because the rules changed a few years ago.
All the best in your flying!