Advice on installation of O2 sensor on 73 115?

[Kevin Trent <trentkc@domain.elided>]

I want to install an O2 sensor on a Spica injected '73 Berlina so I can use 
a Dynograph to fine tune the mixture after my soon-to-be completed  engine 
rebuild.  My intent is to use the Dynograph as a diagnostic tool, not for 
on-going use, and will eventually want to install a "bung" on the exhausts 
of all my 105/115 alfas as the opportunities arise.  When not in diagnostic 
mode, I'll want to remove the O2 sensor and cap the bung without leaks.

It is my understanding that to work properly, I'll need to install the O2 
sensor before the front muffler, which leaves only one of the two head 
pipes (1-4 or 2-3) behind the stock exhaust headers.  Finally, I understand 
that I should use a 3-wire sensor with a preheater.   Any other suggestions?

Anyone out there done this?  Have any advice?  Is it worth doing??  Is 
there a cap or plug to block the O2 sensor bung when the system is not in 
use?  Has anyone tuned a 4cyl with Webers using the dynograph as feedback 
on mixture?  How should it be wired?  Thanks!!

Kct, Powell, TN 
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