I understand what you are saying. for such light marks you do not need to weld because there is a very good chance of cracks developing and the head becoming twisted. So what I suggest is to "lap" the head. Get the following items:
1 - Thick glass about 1.5 times bigger than the head. Thickness of the glass to be 8mm or more.
2 - Grinding paste. This has two grades of paste in the same tin. One side is fine and the other side is coarse.
3 - A bit of kerosene or diesel. This will be required to get the coarse paste a bit of movement.
See the picture below:
What we are going to do is to basically sand down the aluminium to the point that the dents are removed. To ensure that the surface is level you will have to "lap" the surface. In order to do that you will have to remove the two dowels (#1 & #2). You have to make sure that the valve guides are below the aluminium body of the head. If not, then the lapping process will not work. I don't know if you would want to remove the guides. I will advise against it. If the guides are below the metal face and when you turn the head over and place it on the glass, if the guides do not touch the glass you are good to go.
Lapping process involves placing a fair amount of the coarse grinding paste on the glass, a bit of diesel or kerosene and then moving the head on the glass in a figure "8" motion. The idea is that while the head is sanded down it remains totally flat and even. Once the main dents are gone, you have to finish the job with the fine paste. In this way, only a very small amount of the aluminium is removed and the head remains flat.
