Newbee dumb question, What exactly is B stock

I suppose it all really depends on the product you are
buying. In some cases - such as racks or speakers - it
may mean that certain parts don't have an exact color and/or
finish match. With electronics it can be a dealer demo
unit, a unit that had some type of problem (either mechanical and/or electrical) and was returned to the
manufacturer for repair and/or refurbishing, or possibly
a discontinued model that the manufacturer wants to unload
at a discount.
It should be clearly noted that most electronic items
tend to fail within the first 90 days of use - if they fail
at all. If an electronic unit has been repaired and then
sent out for sale as a "B" stock unit - it may often have
a new item warantee - and should function as new.
I personally DO NOT consider any item being sold as a
"scratch & dent" item - especially consumer electronics -
as a "B" stock units. Most of this stuff has been either
been damaged in shipping or by the dummy employees of an
electronics store. Save your cash and time - and avoid this
junk at all costs. In most cases - even if the item functions well - it's appearance will be a constant sore
point and make future re-sale a problem.

'B' Stock...a pair of "stock" McCullochs bolted onto a Dart chassis, using G.E.M. cans, Max-Torque clutches, and Azusa sprockets...Anyone know about THIS?

I guess you need to know how B stock? Factory B stock with a factory warranty is a much much safer bet, than B stock that was "refurbished" by a 3rd party and carries a 3rd party warranty.