My house has T-111 type plywood panel siding on it. When it was
installed long before I bought the house, on an addition it was
installed much too close to the ground. Unsurprisingly, in these
areas, the siding has rotted and is falling apart.

Because the foundation of the addition is not nearly as high as the
original house, the only way to fix the problem is to regrade or find
another answer. For various reasons, regrading is not possible. So I
want to cut off the bottom 10" or so of the siding and replace it with
something more resilient like pressure treated lumber or cedar. The
idea is that either will be more resistant to rot and insects, and
further can be easily replaced in the future if it does succumb to the
elements.

This raises two issues: 1) I'm having trouble finding z-flashing that
accommodate anything thicker than 3/4" combined with 2) which is that
that I'm having trouble finding pressure treated or cedar that is
thinner than 1".

Ideally I'd have this board be the same thickness as the siding (3/8"
or 5/8" probably), but I don't think I'll find that. Any ideas where
to find 1" z-flashing?

Also, any suggestions for how to affix the z-flashing under the
existing siding edge given that I'm installing this 'backwards'?
Usually you'd start from the bottom and go up, so the flashing install
is simple.

Will pressure treated accept a solid-color stain well enough to blend
with the rest of the siding?

Comments on the whole plan or suggestions for alternatives are
welcome.

thanks