The originals are available as are the Ford units if you want to stay old school. If you are running 12v there are the readily available Runtz devices from any number of places. I don't know how they are constructed but expect it is nothing more than something like a 7805 arrangement with a constant 5v out. Downside to those particular units are the expense of one unit needed for each gauge.
I have a couple of concerns about the constant voltage output to the old school bimetal strip gauges which would not an issue on the magnetic type gauges like some Packards used. On bimetal types, will the constant power that does not allow the bimetal to cool slightly between pulses cause the gauge to read higher than it would over a period of time or will the gauges by not having the larger voltage delivered in spurts to heat the strip not need the cooling off to average out the deflection.
Craig experimented using a Drok type converter to run his Panther project cluster. That seemed to work well on the bench but he hasn't got the car on the road yet to know about gauge stability or any long term issues. I wouldn't think there would be any issues but without any experience the question still sits in the back of my mind. If you went with the Drok you might be able to answer the question. Here is Craig's thread with what he used if you want to try the Drok. The Drok he used does look to be less expensive than the old style chopper.
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