I beleive it will not help you under 6500 rpm with that mild cam. The rev kit helps keep the lifter rollers from flying off the cam lobe at high rpm so they don't get hammered. However, you can still have valve float as low as 5000 to 6000rpms and this is due to poor spring control and the valves bouncing of their seats when they close rapidly due to the more agresive roller cam lobe profile. I have a rev kit and a mild hydraulic roller cam and it didnt help at all, as I still had valve float at 6000rpm. I am no expert but I am working through this issue and have found very few experts even at the cam companies that can give good advice. Telepohone jockeys are useless. On a hydraulic roller, I now beleive the valve spring seat pressure is key to keep the valves from bouncing off their seats, but do not exceed 150 pounds on any hydraulic roller or you will just end up collapsing the lifter. I am going with 140-145 pounds on the seat. Most cam companies do not recommend enough seat pressure, suggesting less than 120 pounds. You could probably sneak by with your set up with a tad less seat pressure than 140-145, but I would not go less than 130 pounds on the seat. I would also try to keep open pressure not less than around 300, but not more than 350 pounds.
Your rocker arm ratio will also be a factor. I don't think you need the rev kit (bitch to install, too) with that small a cam in a 406 since your max RPM will be well below 6000rpm, but pay careful attention to seat pressure. Also, when adjusting the lifter prelaod/ rockers, do not go more than 1/4 turn and definitely not more than 1/2 turn on the preload. It will rpm higher by minimizing the preload.
Again, I am no expert..but I had trouble finding good advice on this issue over the past year and this is what I have learned.
1973 RS Z28: Littlefield race series 6-71 supercharger on a 355 w/ AFR 195 heads, 12-14 lbs boost, 7.6:1 static compression, CompCams hydraulic roller (276/288 advertised, 224/236 @.050 duration, .510/.527 lift w/ 1.52 rockers on a 113 lobe separation), AFR Hydra-Rev kit, Eagle 4340 Forged Steel crankshaft, ARP studded bottom end, Eagle ESP H-beam rods, TRW forged reverse dome pistons, Comp Pro-Magnum 1.52 roller rockers with 7/16 studs, twin 750 Edelbrock carbs, 1&3/4 inch Hooker Super Comps, 3" dual exhaust with cross over pipe. MSD 6AL ignition & Pro-billet distributor, Tremec TKO-500 5-speed, Moser 12 bolt with Eaton posi, 33 spline axles & 3.42 gears.
1973 RS Z28: 401ci Dart Little M, Littlefield 8-71 supercharger @14lbs boost, Callies Magnum crankshaft, Lunati Pro-Mod rods, JE pistons, 7.8:1 compression, AFR 227 Comp heads, T&D 1.6 shaft rockers. Reed solid FT cam (240/250@.050, .523/.542 lift, 112 LSA), QFT 750 carbs, Lemons headers, Mezier mechanical water pump, Tremec TKO-500 5-speed, Moser 12 bolt, 33 spline axles & 3.42 gears.