Try new wires and caps, especially if they are the original. When it dies, when you first key on, do you hear the fuel pump for a few seconds?
There is a lot to the carbs and if you don't know what you are doing you can really mess them up even worse! There is a really good video out occasionally available on Fleabay on rebuilding them. The video is about VMax carbs but they are basically the same. I would try a good dosage of Seafoam and drive it like you stole it. Works wonders. You can pull the diaphragm covers and inspect the diaphragms for pinholes and replace any with holes without messing anything up, but chances are the carbs will need some kind of service.
Yes, try new plugs as they do tend to go south rapidly. You say it had spark so rule out electrical problems unless you want to try all 4 wires the next time it happens.
I would drain and flush the gas tank, you may be contaminated with bad gas or just plain crud. Another possibility is a bad fuel line, especially the one from the fuel pump to the carbs...