Thanks for the very interesting info.  With what
you and others have said, I think the best course
of action will be to take the guts out of an M38
and an M76 (each in BA42A cabinets), and move
them over to the BA43B cabinets, and attempt to
cobble up some 5 device A bus cables for dual
scsi controllers.  That will maximize speed, on
the older hardware (until I find that mystical
4000-705A thingie....(:+}}...), and maximize the
internal drive space.  The leftovers will get
packaged up in the A cases and used as door prizes
at our local BSD users group monthly meetings.
(That is a nice thing to do with leftover Sparcs
and VAXentoyz.....(:+}}..., everyone needs a VAX
door prize, right?).

Thanks for the input.

Bob