No need for coding....
Choose your head unit, making sure it is supplied with a powered dab Ariel.
Go to here
https://incartec.co.uk/Ford/Transit-Custom-EuroSelect your make of headunit, then make sure you select a facia adapter for double or single din whichever you decide.....
Their kits are totally plug and play and make head unit installation a breeze. Order also an Ariel adapter, steering wheel interface (often included in their loom but sometimes separate)
If in any doubt call them they are very helpful (if they are open during this chaos of course)...
If you still have any doubts reply back with the unit make/model you are getting and I’ll advise what is needed.....