With this wonderful flash and lens, any 5D will works perfectly. I like 50mm primes on FF, could use only this prime and no other lens for weeks.
I would recommend to add Tamron 28-75 2.8 later on to have additional range. Good IQ, small size, weight and price also light. Again, if not 50 prime, this will be my second choice to have only one lens on FF camera.
I like this lens on my 5Dc for portraits with little hint from flash and for walkaround.