The only problem is, when installing a new pushrod, the valve lash has to be adjusted. That has to be done with the valve cover off. Both jobs can be done topside. The push rods will come out the top when the rocker is out of the way. And they will go right back down into the lifter.

Pulling the push rod cover would let you eyeball the push rods better, but is a good bit more work than removing the valve cover.

Maybe there is a trick to installing pushrods frm the pushrod cover I don't know about. But it must be tricky to set that valve lash.