Edelbrock LD340 Intake Manifold Usable Max RPM?

I know, right? Anything near those specs today they want about 170# on the seat and over 400# open. Stock spring diameter is 1.430" and I cut the seats to use a 1.480" diameter spring installed at 1.750. I don't recall who made the springs - I bought all that stuff from Ed hamburger way back when and trusted his recommendation. I set it up just as he said and never once ran into valve float even with only 130# on the seat.