Vss on 165 ecm help!

[Mike Rolica]

I have one last thing to solve on my tpi s10 project.  I have a mech
operated speedo and the prom is for 89 firebird 350 tpi   (apyu)  It has one
wire -Brown for the vss.
With the ign on I have 13v nothing connected.  I've tried the optical type
but most I find are bunt out and I believe they are only dc pulse.  What do
I need to send to the ecm?  What is it looking for in detail.  I have and
inline gen. used on my 84 jeep grand wagoneer.  On my fluke meter it reads
4v ac.  how can I make this work?   And I am sure I will shoot someone if
they start telling me to modify the code of go buy something from JTR. ;-)

thanks, Mike R