You might want to just install the 85 speedometer into your 85 instrument
cluster.
The connections to the main plug, T14 are different between 84 and 85.
It's not hard to swap wire positions around on T14 ...
but for pure 'no wire thinking' ...just swap out the speedo.

for example......oil pressure warning light switch ......on the 83/84 it's
at T14/10 ( page 97.56 on Bentley ).
On the 85 it's on T14/13 ( pg 97.62 )

the T14 plug opens up ( nicely ! ) to swap wire positions , so not 'too
hard' to make the changes.
Other wires besides the OP switch circuit or different too probably.

Scott

----- Original Message -----
From: "Jamie Fitterer" <fittdog8848@HOTMAIL.COM>
To: <vanagon@GERRY.VANAGON.COM>
Sent: Tuesday, April 13, 2010 5:22 PM
Subject: Re: 1984 Speedos

Yeah.....I have an 85 Instrument panel that I just haven't had the time to
put in.  My "tolerance" is about 15.3. LOL.

> Date: Tue, 13 Apr 2010 19:43:28 -0400
> From: dbeierl@ATTGLOBAL.NET
> Subject: Re: 1984 Speedos
> To: vanagon@GERRY.VANAGON.COM
>
> At 07:41 PM 4/13/2010, Geo wrote:
> >There is even a formula in the Bentley (p 90.30) for the 84 model year
> >to compute your actual speed based on what the instrument says.
> >Pretty handy... if you happen to have a calculator in hand while you
> >drive.
>
> That's a tolerance, not a conversion. But in '85 they went back to
> speedos with a much tighter spec in US Vanagons, presumably by customer
> demand.
>
> Yours,
> David
                                          =