6S6, don't forget that if you change the voltage for one meter, you change it for all three- you may fix one and screw-up the others (water, oil, fuel).
I found that aftermarket "solid state" voltage regulators don't work as well as the OEMs in this application. The original is a bi-metal device that opens and closes repeatedly. It is made to be on and off for a specific time to give you 12v pulses that equal about 5v over time. The meters don't care if it pulses, because they are bi-metal devices too, and respond slowly to changes in voltage. When first turned "ON", the OEM regulator takes longer to turn "OFF" on the first pulse. This gives you more "ON" time at 12v and makes the meters come up to their actual setting quicker than an aftermarket regulator. That probably isn't consequential for anything except oil pressure. Most people like to know as soon as possible if the engine is getting lubricated. Depending on where on the scale the needle will swing (low, med, or hi), it can take 1.3 to 4.1 times longer for the "solid state" regulator to get the needle to its operating point than the OEM regulator. It was 2.72 times longer on low, 4.1 times longer on medium, and 1.3 times longer on high. That's pretty significant... but maybe I'm the only one that cares!
