Welding is probably the easier way, if possible, try to make the weld joints where they can be easilly ground down if you decided to remove the connectors.
I told chryco that I put a set on my hemi back in the late 80's . They were 2x3 box moly steel . They stood out like a sore thumb and I had to hack up a perfectly good floor pan. If you can get form fitting like he describes, You could spoy weld the floors to the tops. Then drill / cut the spots out and wled the holes shut later.
If you can get your hands on ceramic backing squares , they work fantastic for holding the weld puddle in place while back filling holes. They come in a large variety of shapes and sizes. They don't melt and the weld doesn't fall out so it makes filling holes and large gaps a lot easier. :thumbs:
