I run Eddy's and think the base springs are a bit weak for that cam lift. It does depend on ramp speed and I suggest you call Howard's and talk to somebody else... they should be able to give a recommendation.

When I started pushing my fast rate .55" lift cam on the track I upgraded to a Comp double spring. Under 6000 RPM I was probably OK with the single Eddy spring but I occasionally ran it up to 6,500 and did not want to find out the hard way I needed more spring.