Your optimal choice would be a late series IIA which had the same basic wiper setup as the Series III and early Defender.
As Chris points out you would need the Series III windscreen brackets to support the defender windscreen and you could fit the Defender instrumentation to get correct readings. You would probably need new tunnel sheet-metal and floors which could be custom, but made to bolt in if done correctly.
Sarek in Richmond VA fitted a digital configurable dash to a IIA, that was fully programmable.
I don't know many details, but if you think about it an electrical sending unit is just an electrical transducer that sends a voltage signal based on an electrical measurement of temperature for example.
There is a predictable scale of voltage that needs to be configured and the result is a processed image.
The setup worked out very well.
I do have to ask, isn't the Defender unique enough without having to have a unique Defender?
Because, a Defender with a Series dash would be very unique, but with the right parts and pieces would bolt right up.
The reason I have commented on this post is because this fits into a theme that I have had for well over 40 years.
That is if can bolt on/in and unbolt, then it is a reversible change and in my mind an acceptable non-invasive add on.
It's effectively a non-mod, mod oxymoron, until It gets unbolted, and then it's gone.
This concept has been built into every engine conversion or other mod I have put on to one of my series or Defender vehicles.
The mod is a mod, until it is unbolted which allows the vehicle to be restored to it's original configuration.
This has always been a mandatory requirement for anything and everything Land Rover, with only 1 exception, with all the kits and pieces during a lifetime of building Rover upgrades.
This perspective makes you go to a lot of extra trouble and often results in exerting time and money to reach a dead end because if it can't be made to bolt in and out, then it does not meet our standards.
With all the "builds" and engine conversions going on, most owners rarely consider or even care about the consequences of making what I call irreversible changes to a fully original vehicle. Yours could have the later IIA wipers like the stock Defender mentioned earlier.
I have taken this tangent far enough, but will end with some of the builds have been awful and we won't touch them.
In the meantime, we;ll keep building and installing our bolt in conversions.
Going back to the original them of this thread, it can be bolted in with the right components and here are a few pictures of the Sarek dash set-up on an early IIA with separate wiper motors that bolt to the top of the windscreen.
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