Who is going to do the work and how???

I will be. But that doesn't tell you much, since you don't know my
work, past experience, training etc. I do happen to be an engineer by
training, sort of, which still tells you nothing, because there are a
lot of mechanically disinclined engineers out there.

While one could certainly figure out a way, not going to try w/o seeing
directly to comment on this. Sounds to me like would be more effort
for apparent little gain -- is that extra foot of clearance possibly
gained of any real necessity?

Yes, the clearance would be very helpful. We are going to be pouring
and finishing a large concrete slab (one that extends right through
this opening, actually), and I imagine it will be a pain enough trying
to finish the part of the slab that goes through this opening. Don't
ask why we are doing this... I'll post some pictures in a week or two
of either a completely failed project, or a crazy but successful
project to rehabilitate an old garage.

-Kevin