There are a few different web sites with DIY versions oF the tach adapter.
I have found after a little research a cheap tach adapter $10 plus postage.
This small board adapts a Tachometer to up to 4 individual coil packs, capable
of handling 4, 6 or 8 cylinder wasted spark applications
Installation is straightforward:
* Connect Coil 1,2,3 and 4 to the drive signals to each coil packs as necessary.
* Connect the tach output to the input of your tachometer.
* Wrap the board with electrical tape or shrink tubing- the board is small enough
to integrate into your wire harness / bundle.
Here is the the web address
TachAdapter - Autosport Labs
I have purchased one from their website with paypal.
So I will try it when it gets here in about 2 weeks time.
This could be used on other vehicles for engine swaps etc.