I removed the chrome trim from my 70 that runs along the doors (beneath window) and top of fenders. Now I have a bunch of small holes from the screws. What is the best way to fill these in.

Mig weld

Yes the best method to repair those holes is welding them shut. If you just cover them with filler be it regular stype filler or glass stranded filler, all metal whatever, the repair WILL fail. Moisture will attack the filler from the backside, loosening its grip on the metal causing it to pop out and start rusting.

What I like to do to those holes is put a slight bevel in them. By putting that bevelled edge on the hole you gain surface area for the weld to "stick" to so when you grind the weld flush you wont run the risk of grinding thro the welded repair. I take a tapered punch and very lightly hit it with a hammer to bevel the edge, its a good idea to back up the hole from the backside with a socket or something. Now you can weld the hole shut.

Another sweet trick is use copper for backing when welding the holes. The weld wont stick to copper which will allow you to weld up that hole much easier and plus the copper acts like a heat sink. The copper will absorb some of the heat making for less warpage on the surrounding metal.

Take your time when welding them holes, dont go down the line when welding, move around. Say do the front hole on the fender then the last hole then middle hole, wait a few minutes then start over.

Plus NEVER EVER use cool water or compressed air, oil whatever to cool the weld. Doing so will shock the metal making it work hardened and ultimatily brittle. Some say doing this will make for less warpage which is not so, allowing the metal to cool naturally is the best way to prevent warpage.

When welding the effected metal expands but cant do so cause the surrounding metal is cool and wont allow the metal to expand so it expands upward in the form a bulge,now you pour on that cool water you SHOCK the metal into that position. So leave the metal alone allow it to cool by itself...Eric