Dual output alternator.

I have a dual output alternator on a 400000 series 2 cyl. One wire coming out of the stator supplies 14vac to the headlights and the other wire has a diode in line to charge the battery. Is it possible to use a regulator from a higher amperage stator, cut out the diode and feed both stator wires to the regulator to get more charging amperage? I would think it would be better for the battery to have regulated voltage.

Lead acid batteries are not that sensitive to unregulated voltage. What they don't like is leaving their voltage drop... sulfatation start below 12.3V and a battery below 10.5V is dead (even if you can recharge it, most of the capacity is lost / CCA will be way lower / other problem can occur (high self discharge rate, etc)).

Which problem you try to solve ? What is the usage of the engine ?

Depend of the regulator, but it will probably need rectification before. With 14VAC you will need 4 diodes, with single diode (half wave) voltage will be too low.
Voltage of light and charge coil are not the same I think.

Adding a regulator won't increase amperage. You need to upgrade the system. The dual circuit alternator works well as long as electrical accessories are not added.