Re: Advice on body work / filling holes?
This is just a suggestion, I left the lights on my bus and painted over them, but this is how I would approach it if I wanted to remove the lights...
After the lights are removed, find some thin steel and cut some discs slightly larger than the light hole. The idea is that this disc goes on the inside of the bus and gets welded to the edge of the holes the lights used to occupy. This gives a nice flat surface. At that point I would not be afraid of using body filler to build up the 1/8" or so thickness needed to bring the whole panel level. You can use a grinder to bring the weld down to the level surface.
I used body filler on all the holes that were left after the stop signs were removed and any other unwanted holes, many larger than 1/8" and have not had any problems. I typically use the 3M products and buy it by the gallon, a gallon will last for years. You probably only need a quart or 2.
I have most of my problems with the body filler if it is left exposed to the elements. About 3 years ago I did some body filler repairs to 2 different vehicles. The one I painted right away, my truck I was lazy about and it sat for 3 years until I finally finished painting it this weekend. The exposed filler cracked and chipped along the edges. I sanded most of the old filler away and then re-did it. The other painted car that was done at the same time has not shown any sign of cracking or anything, and on that job the body filler has some spots approaching 3/4" thick.
1988 Chevrolet S6000 8.2L Detroit Diesel