As for the lights... Those headlights work on both AC and DC, a bulb is nothing more than a resistor, it doesn't care what the power is, only the voltage. If you were to run 115v through them they would burn out.
On the Tecumseh you should have a two wire plug. If you still have the wiring from the snowblower you should see that one wire went to the light switch, the other went direct to the other side of the bulb. Take the one that came from the switch and put a diode inline with it and a 3a fuse and connect to the positive battery terminal, or the battery side of the starter solenoid, a good 5a diode is what i usually use for the engines with the 3a coil, or a 5-10a bridge rectifier. Then connect the other wire to ground. If you use a bridge take the two wires from the engine and connect them to the AC terminals on the bridge, doesn't matter which one goes to which, then from the positive terminal put a 3a or 5a fuse inline, depending on which coil you have, and connect it to the battery positive terminal, and from the negative side of the bridge go to the engine block/frame or battery negative depending on how your ground wiring is set up.
Now you have a 3a/5a DC output for battery charging and lighting. The average 35w PAR lamp on a tractor takes about 2.5a to run.
On my Ariens i put in a new Briggs that has a dual output alternator, it has a 5a AC output and a 3a DC output. I use the AC output to run the lighting, and the DC output to charge the battery and run one LED work light which draws about 1.5a and provides more light output then the 35w tractor headlights. A tip on those... They have a red and white wire on the new Briggs Intek, the red is the DC output with a diode inline, the white is the AC output. If you cut out the diode and put the red and white wires on the AC terminals of a bridge rectifier you well get about 13a DC output by using both coils together. I have wired a few like this. On mine i have about 2a of DC draw with the work light and my LED strobes, that leaves 1a for battery charging, so i didn't bother with the higher output. However, if you run the lights off AC just remember they are only available for use when the engine is running and change in brightness with engine speed, if you want to eliminate that then you need to run your lighting off DC so the battery keeps them on.
What i would do in your case is put a rectifier in, run the output to the battery, and then wire the lights through a switch and fuse to the battery. Pull off the AC starter, as mentioned its just a switch in a box on the top of the engine, put on a DC starter and a solenoid and wire up a simple push button switch to crank it over, unless you have a key switch with a starter output on it.
Edited by kb0nly, December 08, 2011 - 09:31 PM.