Regarding 3/260 video:

As far as I've been able to figure out, the 3/260s, despite the hint
in the PROM manual to the contrary, can not run in 1152x900 mode.  I
have two of these beasts, too; so, if you find a way, let me know.  (The
PROM manual indicated that 1152x900 required a hardware mod which
everyone I've talked to claims doesn't exist.)

> My questions, then, are (1) is there any reasonable chance of getting
> the -3/150 to drive its video connector?

You might check that the Video Clock jumper is in place (J2301 - just up
from the keyboard connector).  Otherwise, I suspect you have bad video
hardware.  (Hint for the others, this is the same as a 3/140, 160, 180
and possibly a 75, depending on the exact board.)

>          (2) can the monitor be
adjusted to run 1600x1280, and would it hurt it to do so?

Nope.

>                             and (3) when
> I boot NetBSD on the -3/260 (using the cgtwo it also has for console),
> it reports the bwtwo as 1152x900, why?

It lied.