Are they a self contained unit. Or do you need to poke a hole in the oil pan for the oil return ?

I put a bung in the port side valve cover for the return line. You can see the temporary brass plug in it right in front of the breather.

The kit I had was a standard intercooler set up for an EFI setup with a rectangle to round adapter tacked on to run a carb hat.

Full disclosure - I never ran it though. I thought better of my engine and drive limits and went a different route.