Be careful with Vizard's rule... if you read his books that rule is for factory mediocre heads and flow. If you really read what he has proven on hundreds of dyno runs is the LSA is a function of air flow at low lift, like 0.100. The better the flow at low lift the wider LSA the engine will want. He points at modern high performance 4 valve per cylinder engines have LSAs in the 118 degree range because they flow a lot of air at low lift. I don't know the specs on flow for the heads you have but if you want to follow Vizards building recipe if you calculate the LSA of 108 and those heads flow much better at 0.100" lift than stock his recommendations would be to maybe crank it up a notch to 110 maybe... I know that goes against some of the recommendations here but that is what the math and testing he has done recommends.
Also remember what Vizard IS NOT for making some single peak number like 400 HP. His recommendations are to create an engine that makes the most power across the RPM band, i.e. the total area under the torque curve is maximized not that you will get peak torque or HP numbers.
I have used his math/recommendations on my last 2 builds. The 225 slant 6 I went with an Oregon cams that was 106 LCA because the stock heads flow terrible (I also put oversized valves in but did what he said, err on the side of tight), Dutra Duals with the "Y" 45" back for peak torque at about 3000 RPM and decked the block to get just short of 9:1 compression. It won't make big HP number because I dailed it in to make most power below 4500 RPM but man does it run good in everyday driving. I did have access to performance trends software for these build too so I ran a lot of simulations for the 2 builds. The second is a 360 for the Valiant. I just got that running a few weeks ago and just getting it broken in. I have not really seen what it does so I can't tell how it came out. Again a Oregon cams grind and like you calculated about 108 with the Edelbrock heads but I went with a 110 because they flow much better than stock and the Vizard rules needs adjustment because of that.
With the low LCA numbers you can't run a lot of duration without getting into a lumpy idle and poor vacuum. That will kill lower everyday RPM power but give you the possibility for the 400HP if you plan on running it at 7000 RPM all the time. On the other side be careful with a lower LSA and very short durations and compression. The math says the low end torque is improved but it does be cause the cylinder pressure is growing. There is a place where the cylinder pressure gets too high. The typical 215-225 duration at 0.050" lift will be fine. I was experimenting with lower duration and pressures got to high. Like was said earlier with these smaller displacement engines you really need to pick your poison... do you want to maximize street torque in normal driving RPM or do you want to be able to say it makes 400 HP on a dyno at WOT, its hard to get both.
I personally hate headers and won't use anything but stock manifolds but you can really make a huge bump in the power in the street driving RPM range if you use Vizards math and get the header tube length AND diameters close to the RPM band you want the power. That was clear in the simulations.