I purchased this 6466 turbo from another member for my new build and it didn't come with a actuator. That is why I was asking if internal or external. HD actuator would be the easiest to install. But I don't have a problem fabing up my headers for external
Good luck controlling boost with a HD actuator to 20# with a 6466. You want a light spring in the actuator and mbc.
I'd sell that turbo and go smaller.
Get a 6262 and use internal gate with standard actuator. Open it up to .96/.97 .
Set your cracking pressure 12,13#. Get a MBC and turn it to 20,21# from there if that's the boost level you want.
Good luck