Here's one method I've started but not completed (need more time in the day, and year too for that matter).
https://picasaweb.google.com/118082...lectronic?authuser=0&feat=directlinkUsing the original speedometer housing and adapting new VDO movements to it. I have started on the 85 mph speedometer and will also do a 4,000 rpm tachometer.
I chose VDO movements because they're very easy to setup and program. For example the tachometer I used will work with an alternator signal or a signal from the flywheel ring gear (diesel application). Most other brands sell different tachometers depending on what signal you'll use, but VDO is sort of an all in one deal, and easy to program and calibrate. The speedometer will also use nearly any sort of electronic speedometer signal, and I have a sender in my transmission already so that's easy.
The VDO gauges I have are also easy to adapt to the original housing and the odometer and or hour meter fit within the inner circle of the original gauge face.
Grigg