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old owner put in a 6 volt system in my m37,I can keep it or go to 12 volt ,iam getting a new wire harness from joe at maine.he suggested I put a 12 volt gm 1 wire alternator ,is there a specific one I need,and what else do I need to change to a 12 volt upgrade, I know obviously a battery ,coil, ,do I need to change distributor and starter motor,dont know if the starter is a 6 volt or 12 Ineed to find that out,.....or do I keep it 6 volt and just deal with it,is that a bad decision..any input would be helpful thanks everyone....

I would say make the jump to 12volt. Unless its a more show than go type of truck. It might cost a little more having to change out all your electrical equipment (or at least most of it) but it'll be worthwhile in the long run. You'll need to change the light bulbs (gauge cluster bulbs too) for sure and the starter as a 6 volt starter (motor) will handle 12 volts, but not for long). Most switch's will handle the extra voltage without issue, but I can't give you a definitive answer about the coil and distributor... Don't forget about the fuel tank sending unit either...
An auto wrecker would have lots of single wire GM alternators kicking around, maybe compare a few to get a handle on the size and what will fit in your intended location. Saves multiple trips to the parts store...

Hope this helps...

I disagree about the 6v starters longevity at 12v. As long as you don't have long hard starts on it, the 6v starter will work perfectly fine. The starter will realistically be happier at 12v than it was at 6 since you are pumping less current into it. Plus, good luck ever finding an actual 12v starter for the 230... Apparently Napa had one, but I don't have the part number.

Gauges and senders have to be changed for oil, water, and fuel, and all light bulbs. I don't like the one wire alternators for our application, but to each his own. With such a long run from the alternator to the battery, it makes a lot more sense to run a sensing wire since there will be voltage drop across the main wire, not the easiest solution, but it is a much better solution for overall battery longevity. I can't think of a single advantage to a one wire alternator other than being the lazy way to wire up a charging system. Here's a basic run down if you care to read. but basically you have the one big wire going to the starter, then you have one small wire going to the switch side of the ignition coil, then one wire that follows the main charging wire to the hub. The voltage drop can be significant and will only decrease your battery life and give you weak charging

http://www.madelectrical.com/electrical ... ire3.shtml

I run a single wire 60 amp GM alternator on mine from an '84 C-10 pickup. The drive pulley matches the M37 belt. You'll need to add an "exciter" wire from the alternator main post to the "B" terminal on the alternator so the regulator will "step up" when you hit the gas. If you go to a civilian distributor you'll also need to change your oil pump because the M37 distributor tang is offset, not centered. The fuel tank sending unit can remain intact but you'll need 12V gauges and bulbs, and I recommend 2 12V batteries wired in parallel for plenty of cranking power to a 12V starter. I'd also recommend a battery "kill switch" so you can make all of your electrical circuits totally dead when the vehicle is parked. If your wiring includes a ballast to the distributor then you must use a ballast-type coil or the coil will blow wide open (I learned this the hard way). I used a Painless Performance wiring harness on mine, including a GM-style light switch, and also changed to gammagoat taillights for added visibility.
Gary

The oil and water gauges are mechanical, are they not? No point in changing the gauge when simply changing the bulb will suffice. As for the voltage drop due to the long run back to the battery, its a moot point. Take the lead from the alternator to the main cable at the starter. Does the same thing with a shorter run.
Also, put a 12 volt starter in it with a 12 volt system. Sure the 6 volt might handle it for a while, but why bother testing that theory? You'll get a definitive answer when you least want it.

got a part number for that 12 volt starter that meshes mechanically before the power because I haven't found one...

My oil, water, and fuel are electric, wiring diagram agrees. My speedo is the only mechanical gauge in mine.

I haven't seen a 6v starter fail under normal conditions, many people on here have 6v starters on a 12v system, as do quite a few tractors and other vintage vehicles. Hell, vintage power wagons has a 6v to 12v conversion kit that specifically states you can keep your original 6v starter. It spins faster and draws half the current for the same power output so your engine actually starts better.