All tached out, need wiring help,please Options

[porschetub]

Changing from a 911 641 301 00 (early 70's ) tach to a 911 641 301 86 (911 SC MY 86),the early tach has a different rear plug but both share a 3 wire connection.
Bowlsby (thanks Jeff ) pic shows wire 11 as being red/white as 12V supply ,wire 13 as being earth (ground) brown x 2, wire 12 black /purple I presume is signal from CDI box via relay board ?.

Late tach is #2 to 4 across the top and #5 to 8 across the bottom ,#2,6 and 7 are the only used, help please as me and VDO instruments have never been happy together (IMG:style_emoticons/default/lol-2.gif) (IMG:style_emoticons/default/lol-2.gif) .TIA.

[porschetub]

Thanks Greg and Mark and yes I should have been a bit more clear,I'am running a Ashlock tachadapt with the jumper reinstalled to suit low voltage for the 86 MY tach,the tach I'am replacing was high voltage and worked off the adaptor but was unstable from the get go until it failed completely.
I'am running a 911 Permatune blue CDI from a 75 MY car ,Pertronix ignitor II and correct Permatune ($$$) transformer coil.
What I'am trying to sort is connection to pins 2,6 and 7 so far I have this ;
Pin #2 > black purple stripe
Pin #5 > red white stripe
Pin #6 > brown (earth )
With Pin #2 my wire is yellow as output from the adaptor and the black/purple is the input to the adaptor if that makes sense.
I'am thinking this is correct ?.