What 60' times are you getting?
I have not used the action plus small block intake, but the one I had on my 383 was not much better than the stock intake. The Performer RPM air-gap should provide more top end without hurting low end torque, and the air-gap will keep the mixture cooler.
I think if your going to rev over 6,200 RPM, then a solid lifter cam, and stiffer valve springs would be the way to go, but you may be able to get a bit more out of the hydraulic cam with adjustable rocker arms, and titanium retainers?
Advancing the installed position of the cam will just move the torque curve down to a bit lower RPM, so it may help ET, but not MPH.

Take a look at something like the Hughes Engines HTL4852AS Solid Lifter cam. Specs are 248/252 duration @ 0.050", 0.563"/0.572" valve lift with 1.5:1 rocker arms, 106 LSA installed +3 at 103 degrees. The RPM sweet spot is listed as 2400-6200 RPM.