I came up with two sets of driving lights. One set is 100 watts and the other 150 watts.

The 150 watt will draw 12.5 amps. I would fuse this as a resistive load at 2-1 0r a 25 amp fuse.

Will my existi g wiring and relay handle this? Worrying about wirin g capacity. Dont want to burn the insulation off the wire.

doubt it.
Most of the wiring is rated for 8, 15, or rarely 20 amps.

when I did my 911, I ran all new power to the relay and lights...

Put a relay out front (Pelican sells a simple kit) and run new power from the fuse box input side to the relay up near the headlights...simple.

Rich

You are asking 40 year old wire to run modern lights. The wiring is not rated for the amperage. It never was. All automobile manufacturers use wire barely big enough to run anything.

Run a new wire and fuse from the battery with a new relay. Most Bosch style relays are rated for 30 amps.

you dont need to go all the way back to the battery, you can just sister up the new poer lead at the fuse panel input side red wire.

Shorter run....but put in a fuse etc.

rich