Flathead Ford valve train questions

[hotcoupe]

Hello, I took a "59" block to the machine shop recently along with some new internal components, among the supplied parts were a set of N.O.S. Ford hollow lifters. I'm a little gun shy of the current Johnson style lifters, improper material or heat treatment, causing the lifters to fail. My question is, do I need to use a custom length valve, I speced a Manley 1.6" Pro- flow valve. Does anyone have any practical experience in this situation.
Thanx,
Tom