Zimmy,
I think you probably have a bigger problem than you think. From my understanding, 427s can be equipped with either solid or hydraulic lifters but if if solid lifters were used, the lifter
oil galleries were plugged. If you're switching from solid lifters to hydraulic lifters and the lifter
oil galleries were correctly blocked off, you now need to unblock them. Otherwise there's no
oil getting to the lifters and they'll never pump up. Usually the lifter oil galleries were plugged by installing allen head plugs in the short galleries tapping off the center oil gallery. You need to remove the top allen head plug and you should find another allen head plug below it. Remove the bottom one and then reinstall the top one.
You can read more about this in Steve Christ's book titled, "How to Rebuild Big-Block Ford Engines."
Hope that helps. Good luck.
Chris