what welder for floorpans?

I have 70 swinger that has a slight problem. It appears at one time or another the passenger side of the car;s rear shock broke through the floor. The funny part is the floor and trunk are solid on this car. To repair it someone welded in a washer with a mig welder to strenghen the metal around the hole for the bolt although they only welded it in 4 spots at 12,3,6,and 9 o clock. Well before i get it painted i had the great idea to complete the weld and grind it down to look a little nicer than the previous owner did. I was using a lincoln welder generator and stick welding with 6010 rod. No matter how low i set my welder i kept burning through and making bigger holes around it. I can weld with the best of them on anything 3/16" with this stick welder but never tried anything this thin before. I finally gave up and figure i need to just go buy a cheap 110 welder for sheetmetal. What seems to be the best welder for doing this? Any tips on finishing the holes? thanks