I use
Hella and Cibie H4 housings in my VW's. They have an excellent beam pattern and cutoff.
Your harness should handle a stock 60/55 watt bulb. On my vehicles I do add
relays to take the current off the switch and provide maximum power to the lamps. I noticed a difference after adding the relays.
For the stock 6 volt guys there are 6 volt
bulbs and
relays available.