Truss Calculations again...different issue

Ok, my 10,000lb reactions per point load on the garage dormer trusses are known to require a 3-1/2 cubed footing of concrete to support the load. So, I have the tough job of cutting into the garage floor, digging a big hole around and under the existing perimeter foundation footer of the garage, and pouring a lot of concrete and rebar. It's been suggested that I go ahead and consider cutting through the existing footer to make the job easier.
But, now I'm interested whether or not the two 8' long 4x12 garage door headers (plus double top plate across both) can support the point load of the trusses. I can't figure out how to convert reactions numbers into load or forces down on the header. Span tables aren't of any apparent help. Obviously, I want minimum deflection and no structural breakage for these headers.
I have been told by my truss designer that my 2x4 stud wall will hold the point loads, so it seems possible, but I'm still concerned about whether the headers can. To clarify, I have two 8' wide garage doors with 4x12 headers, and a central 8" wide post of several 2x4s (I may swap this out for a 3" steel post, swapping headers is more difficult).
In any case, each door header takes the load of one of the heavy truss point loads, and the point loads of lighter trusses, all spaced 24"OC. I'm trying to solve this while my engineer finds time to fit me into his schedule. Previous help was interesting, so I'd like to understand more about how the trusses will affect my existing headers.
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I cant speak to the other issues other than it sounds like regardless of what you use the footing needs to be increased. If you have access to the entire perimiter of the garage from the outside you do not need to do this from the inside. You can sister on the additional footing next to the existing footing from the outside. In general this involves drilling in to the existing footing at specified intervals epoxying rebar to tie the 2 together plus a bunch more crap. Since you have an engineer he can make up a detail based on the existing footing and what modification you need to make to it work.....that is if you can get him to take your calls.....been there...

Yea and your paying him..dont you love it...
Alan wrote:

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