Calling all 84 Spider owners--speedo cable question

["Greg McNair" <gmcnair@domain.elided>]

Help!  I'm probably dealing with Frankenstein here, but maybe i'm not alone
with this.  My speedo setup is the "split" set of tach and speedo in separate
pods.  I have the "inline" speedometer thingamagigy under the hood, but there
is nothing routed to it or from it.  She stands alone.  There is one solid
cable running from the back of the speedo to somewhere under the
firewall....i'm assuming to the tranny.  The speedo doesn't work.  I removed
the cable from the pod and checked it while rolling to see if it spins inside
the outer sheath.  It doesn't.  I ordered a new "upper" cable, and when it
arrived it had two female fittings...one on each end...to connect the gauge to
the inline thingamagigy.  I figured the single long cable was considered to be
the lower portion of the set, and a previous owner may have bypassed the
inline part because it may have failed at some point.  I don't think this to
be the case anymore.  The current single cable has a plastic female snap
coupler that clips onto the back of the speedo.  The new cable I ordered won't
ever fit the speedo, because the speedo doesn't have a threaded male fitting
to accept the cable.  So what I'm wondering here is, did a previous owner put
in a speedo from a different year that utilized a single-cable system?  Or is
there a male threaded part missing from the back of my speedo?  I'm under the
assumption that the current speedo is not what came with this year model
vehicle, as I can't find a good explanation for why the inline thingamagigy
exists if it isn't being used.  I don't want a Frankenstein setup if that can
be avoided.  But then again, if what I have "should" work, then why doesn't
it?  What part failed to prevent the inside cable from spinning?  As usual,
any help is mighty appreciated.  Now that the rich mixture problem is solved,
she's ready to drive, and I want to know exactly how fast I'm going when
approached by Mr. Blue Lights (it will only be a matter of time...this car
flies, and I have zero self control!)

And hey, while we're at it, can anyone tell me how to diagnose a
non-functioning tach?  I'm presuming it's electric, but I don't know where the
RPM sensor is on the engine.

Greg
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