Engine setting valve lash on stud mounted roller rockers with intake already installed.

Personally I'd wait to install the intake until after you get the pushrods installed. You have to make 100% sure the pushrod is seated in the center of the lifter cup. With the intake off, you can visibly see where the pushrod is making contact with the lifter. IF you do put the intake on, and then add pushrods in, you just lose the ability to see where it physically rests on the lifter. It becomes more of a 'by feel' process at that point.

As for setting the lash, I would also recommend doing that with the intake off. Since setting lash is also by feel, its more convenient to get your fingers around the pushrod when you have open access to the lifter valley. With the intake on, you can still get your fingers on the pushrod, but you can only grab the part protruding above the head and under the rocker arm. That's not a lot of room if you have large fingers.

In contrast, adding the intake only takes minutes, at which I'd just wait on it until the valvetrain is completed first