Well, I think that you'll probably be OK.
But..,
When it comes to old cars, I have a philosophy that I go by: Make sure that items that can get you killed are in tip-top shape. To me, this includes vital drive train components, brakes, seat belts, and lights and lighting electrical.
If you're going to upgrade the lights past what the factory had in mind with it, and halogen's definitely fit that bill, I think you should upgrade the wiring to go along with it. Advance Autowire makes a nice kit just for this. I used this very same kit when I installed my Cibie's (which you might consider as an alternative to the PL700's BTW). When installed correctly, you can't even tell that the kit's there.