I had pmailed this to the OP, but FWIW, this appears to be the part:

http://www.vwheritage.com/vw_spares_Oil-pressure-switch-adaptor-for-waterboxer_act_shop.product_pID_58561579_lang_EN_country_GB.htm

Just in case anyone has super human eyes and can confirm Alistair's
well educated guess at thread count and OD.    :)

Neil.

On Fri, Sep 21, 2012 at 9:31 PM, Alistair Bell <albell@shaw.ca> wrote:

> I'm sorry I can't recall for sure the thread size of reduction bushing off top of my head, (sender is M10X1.0) but I think it is M16x1.5
>
> alistair
>
>
> On 2012-09-21, at 8:10 PM, Paul Rogers wrote:
>
>> A bolt certainly would work, but I just thought I'd throw it out there and see what responses would come. The list is comprised of some very clever, and smart, people and I find it very interesting to their input. Great bathroom reading stuff and that's not to be taken like I'm inferring it's crap.

-- 
Neil n

65 kb image Myford Ready For Assembly  http://tinyurl.com/64sx4rp

'88 Slate Blue Westy to be named.

'81 VanaJetta 2.0 "Jaco"  http://tubaneil.googlepages.com/

Vanagon VAG Gas I4/VR Swap Google Group:

http://groups.google.com/group/vanagons-with-vw-inline-4-cylinder-gas-engines