[sdiy] TTSH - part/substitution questions

[John]

I'm in the process of speccing out a TTSH build, and there's a couple
things I'm curious about and hoping that someone more knowledgeable
than myself might be able to offer some insight on:

First, both the TTSH and the gate-boost BOM list ferrite beads with a
part # of FB_226 - but I cannot for the life of me find any such thing
online. Even a quoted-literal search returns nothing but results point-
ing right back to these BOMs. Is this some understood shorthand for the
specs on a generic ferrite bead? How does one read that?

Second, I'm sure I'm not remotely the first person to note that some of
the transistors required are, erm, unicorn poop, either completely un-
available outside of eBay or just wildly expensive :/ I'm curious, has
anyone worked out alternatives for these?

The 2N4392s are in the electronic switch, and go straight to the jacks;
AFAICT, they're just there to alternately restrict current flow on one
of the two paths?

The 2N3954 is a dual JFET used in the sine shaper; can two JFETs of
equivalent specs be used in its place, or is it important that they be
inna-can for tempco/symmetry purposes?

The 2N3958s go to what were discrete modules on the original. Per what
I can find, one is a buffer for the filter circuit; from my amateur
guesswork, it looks like it uses the ladder's output voltage to control
current flow between +15V and the offset trimmer (which I assume goes
to ground or -15V?) The other is in the S&H, and it looks like it may
serve *almost* the same function, except that it has source & drain for
one JFET reversed, where the filter has them both going the same way.
Is tempco/symmetry also important for these? If they're not matched &
coupled, would that manifest as asymmetric output, or a gap around 0V?

The BOM lists MJE182 and MJE172, which appear from what I can find to
be power transistors, but I don't see them in the power-supply section
and can't spot them anywhere else on the board diagrams I've found. If
I'm using a separate PSU, can I omit them?