bed bolts question

[chucks1967]

So I recently bought a bed that needed a little work on the inside panels down around the lip area where the bed bolts down to the wood floor. They were totally rotted out. I cut out the rusted out area and welded in some sheet metal that I had bent at a 90 degree to mimic the original shape. It looks perfect but the one thing I did not take into account was the bolt holes. They are square to hold the square head of the pan bold. Does any one have a good idea as to how I should proceed. Should I just get a spline type bolt and drill a round hole or just a standard hex bold, or if someone has some way to punch a square hole that would be great. As many ideas and helps as I could get would be appreciated. Thanks in advance.
here is a pic of the job before I cleaned up the weld and shaped the end.