An alternator produces electricity and a regulator regulates the amount of electricity it produces.

Which is better and why? I don't understand your question. They are used in conjunction with one another.

Whether the '55 engine is 12V depends on if it was from a car or a first series or second series truck.

Your truck can easily be converted to 12V if you want 12V wipers and radio. You can use either an alternator or generator. A generator will be fine with just those accesories. If you go to adding things like A/C, power seats/windows and the like, go with an alternator.

"It's just a phase. He'll grow out of it." Mama, 1964

1956 Chevy 1/2-ton 3100
1953 Chevy 6100 "The Yard dog"
1954 GMC Suburban Now with a new proud owner.